The Online Library of Liberty

A project of Liberty Fund, Inc.

• Dedication
• Preface 1
• Translator’s Preface
• Translator’s Preface to Second Edition
• Introduction [p. 1]
• I: The Idea of Transcendental Philosophy
• II: Division of Transcendental Philosophy
• I: The Elements of Transcendentalism
• Part I: Transcendental Æsthetic [p. 19]
• Section I: Of Space
• Section II: Of Time
• Part II: Transcendental Logic [p. 50]
• Introduction the Idea of a Transcendental Logic
• I: Of Logic In General
• II: Of Transcendental Logic
• III: Of the Division of General Logic Into Analytic and Dialectic
• IV: Of the Division of Transcendental Logic Into Transcendental Analytic and Dialectic
• Division I: Transcendental Analytic In Two Books, With Their Chapters and Sections
• Book I: Analytic of Concepts
• Chapter I: Method of Discovering All Pure Concepts of the Understanding
• Section I: Of the Logical Use of the Understanding In General
• Section II: Of the Logical Function of the Understanding In Judgments [p. 70]
• Section III: Of the Pure Concepts of the Understanding, Or of the Categories
• Chapter II: Of the Deduction of the Pure Concepts of the Understanding [p. 84]
• Section I: Of the Principles of a Transcendental Deduction In General
• Section II: Of the a Priori Grounds For the Possibility of Experience
• I: Of the Synthesis of Apprehension In Intuition
• II: Of the Synthesis of Reproduction In Imagination
• III: Of the Synthesis of Recognition In Concepts [p. 103]
• IV: Preliminary Explanation of the Possibility of the Categories As Knowledge a Priori
• Section III: Of the Relation of the Understanding to Objects In General, and the Possibility of Knowing Them a Priori [p. 115]
• Book II: Analytic of Principles
• Introduction of the Transcendental Faculty of Judgment In General
• Chapter I: Of the Schematism of the Pure Concepts of the Understanding [p. 137]
• Chapter II: System of All Principles of the Pure Understanding [p. 148]
• Section I: Of the Highest Principle of All Analytical Judgments
• Section II: Of the Highest Principle of All Synthetical Judgments [p. 154]
• Section III: Systematical Representation of All Synthetical Principles of the Understanding
• I: [of the Axioms of Intuition 1 Principle of the Pure Understanding
• II: [ Anticipations of Perception
• III: [ the Analogies of Experience
• IV: The Postulates of Empirical Thought In General
• Chapter III: On the Ground of Distinction of All Subjects Into Phenomena and Noumena
• I.: Identity and Difference
• II.: Agreement and Opposition
• III.: The Internal and the External
• IV.: Matter and Form
• Note On the Amphiboly of Reflective Concepts
• Division II: Transcendental Dialectic In Two Books, With Their Chapters and Sections [p. 293]
• Introduction: 1.
• Book I: Of the Concepts of Pure Reason [p. 310]
• First Section of Ideas In General
• Second Section of Transcendental Ideas [p. 321]
• Third Section System of Transcendental Ideas [p. 333]
• Book II: Of the Dialectical Conclusions of Pure Reason
• Chapter I: Of the Paralogisms of Pure Reason [p. 341]
• Chapter II: The Antinomy of Pure Reason
• Section I: System of Cosmological Ideas
• Section II: Antithetic of Pure Reason
• Section III: Of the Interest of Reason In These Conflicts [p. 462]
• Section IV: Of the Transcendental Problems of Pure Reason, and the Absolute Necessity of Their Solution
• Section V: Sceptical Representation of the Cosmological Questions In the Four Transcendental Ideas [p. 485]
• Section VI: Transcendental Idealism As the Key to the Solution of Cosmological Dialectic
• Section VII: Critical Decision of the Cosmological Conflict of Reason With Itself
• Section VIII: The Regulative Principle of Pure Reason With Regard to the Cosmological Ideas [p. 508]
• Section IX: Of the Empirical Use of the Regulative Principle of Reason With Regard to All Cosmological Ideas
• Chapter III: The Ideal of Pure Reason
• Section I: Of the Ideal In General
• Section II: Of the Transcendental Ideal ( Prototypon Transcendentale )
• Section III: Of the Arguments of Speculative Reason In Proof of the Existence of a Supreme Being
• Section IV: Of the Impossibility of an Ontological Proof of the Existence of God [p. 592]
• Section V: Of the Impossibility of a Cosmological Proof of the Existence of God [p. 603]
• Section VI: Of the Impossibility of the Physico-theological Proof
• Section VII: Criticism of All Theology Based On Speculative Principles of Reason [p. 631]
• Chapter I: The Discipline of Pure Reason
• Section I: The Discipline of Pure Reason In Its Dogmatical Use
• Section II: The Discipline of Pure Reason In Its Polemical Use
• Section III: The Discipline of Pure Reason With Regard to Hypotheses
• Section IV: The Discipline of Pure Reason With Regard to Its Proofs
• Chapter II: The Canon of Pure Reason [p. 795]
• First Section: of the Ultimate Aim of the Pure Use of Our Reason
• Section II: Of the Ideal of the Summum Bonum As Determining the Ultimate Aim of Pure Reason
• Section III: Of Trowing, Knowing, and Believing [p. 820]
• Chapter III: The Architectonic of Pure Reason [p. 832]
• Chapter IV: The History of Pure Reason [p. 852]
• Supplement I: Motto to Second Edition
• Supplement II: Preface to the Second Edition. 1787. [p. Vii]
• Supplement III: Supplement Iv
• Supplement V
• Supplement Vi
• Supplement V
• Supplement Vi
• Supplement Vii
• Supplement Viii
• Supplement Ix
• Supplement X
• Supplement Xi
• Supplement Xii
• Supplement Xiii
• Supplement Xiv
• Supplement Xv
• Supplement Xvi a
• Supplement Xvi B
• Supplement Xvii
• Supplement Xviii
• Supplement Xix
• Supplement Xx
• Supplement Xxi
• Supplement Xxii
• Supplement Xxiii
• Supplement Xxiv
• Supplement Xxv
• Supplement Xxvi
• Supplement Xxvii
• Supplement Xxviii

Secondly. The principle that realities (as mere assertions) never logically contradict each other, is perfectly true with regard to the relation of concepts, but [p. 273] has no meaning whatever either as regards nature or as regards anything by itself (of which we can have no concept whatever).1 The real opposition, as when A - B = 0, takes place everywhere wherever one reality is united with another in the same subject and one annihilates the effect of the other. This is constantly brought before our eyes in nature by all impediments and reactions which, as depending on forces, must be called realitates phaenomena. General mechanics can even give us the empirical condition of that opposition in an a priori rule, by attending to the opposition of directions; a condition of which the transcendental concept of reality knows nothing. Although Leibniz himself did not announce this proposition with all the pomp of a new principle, he yet made use of it for new assertions, and his followers expressly inserted it in their system of the Leibniz-Wolfian philosophy. According to this principle all evils, for example, are nothing but the consequences of the limitations of created beings, that is, they are negations, because these can be the only opposites of reality (which is perfectly true in the mere concept of the thing in general, but not in things as phenomena). In like manner the followers of Leibniz consider it not only possible, but even natural, to unite all reality, without fearing any opposition, in one being; because the only opposition they know is that [p. 274] of contradiction (by which the concept of a thing itself is annihilated), while they ignore that of reciprocal action and reaction, when one real cause destroys the effect of another, a process which we can only represent to ourselves when the conditions are given in sensibility.

The concept of a cubic foot of space, wherever and how many times soever I may think it, is in itself perfectly the same. But two cubic feet are nevertheless distinguished in space, by their places alone (numero diversa), and these places are conditions of the intuition in which the object of our concept is given, and which, though they do not belong to the concept, belong nevertheless to the whole of sensibility. In a similar manner there is no contradiction in the concept of a thing, unless something negative has been connected with something affirmative; and simply affirmative concepts, if joined together, cannot neutralise each other. But in sensuous intuition, where we have to deal with reality (for instance motion), there exist conditions (opposite directions) of which in the concept of motion in general no account was taken, and which render possible an opposition (not however a logical one), and from mere positives produce zero=0, so that it would be wrong to say that all reality must be in perfect agreement, if there is no opposition between its concepts.1 If we keep to concepts only, that which we call internal is the substratum of all relations or [p. 283] external determinations. If therefore I take no account of any of the conditions of intuition, and confine myself solely to the concept of a thing, then I may drop no doubt all external relations, and yet there must remain the concept of something which implies no relation, but internal determinations only. From this it might seem to follow that there exists in everything something (substance) which is absolutely internal, preceding all external determinations, nay, rendering them possible. It might likewise seem to follow that this substratum, as no longer containing any external relations, must be simple (for corporeal things are always relations only, at least of their parts existing side by side); and as we know of no entirely internal determinations beyond those of our own internal sense, that substratum might be taken, not only as simple, but likewise (according to the analogy of our own internal sense) as determined by representations, so that all things would be really monads, or simple beings endowed with representations. All this would be perfectly true, unless something more than the concept of a thing in general [p. 284] were required in order to give us objects of external intuition, although the pure concept need take no account of it. But we see, on the contrary, that a permanent phenomenon in space (impenetrable extension) may contain mere relations without anything that is absolutely internal, and yet be the first substratum of all external perception. It is true that if we think by concepts only, we cannot think something external without something internal, because conceptions of relations presuppose things given, and are impossible without them. But as in intuition something is contained which does not exist at all in the mere concept of a thing, and as it is this which supplies the substratum that could never be known by mere concepts, namely, a space which, with all that is contained in it, consists of purely formal, or real relations also, I am not allowed to say, that, because nothing can be represented by mere concepts without something absolutely internal, there could not be in the real things themselves, comprehended under those concepts, and in their intuition, anything external, without a foundation of something absolutely internal. For, if we take no account of all conditions of intuition, then no doubt nothing remains in the mere concept but the internal in general, with its mutual relations, through which alone the external is possible. This necessity, however, which depends on abstraction alone, does not apply to things, if [p. 285] they are given in intuition with determinations expressive of mere relations, and without having for their foundation anything internal, for the simple reason that they are phenomena only, and not things in themselves. Whatever we may know of matter are nothing but relations (what we call internal determinations are but relatively internal); but there are among these relations some which are independent and permanent, and by which a certain object is given us. That I, when abstraction is made of these relations, have nothing more to think, does not do away with the concept of a thing, as a phenomenon, nor with the concept of an object in abstracto. It only shows the impossibility of such an object as could be determined by mere concepts, that is of a noumenon. It is no doubt startling to hear, that a thing should consist entirely of relations, but such a thing as we speak of is merely a phenomenon, and can never be thought by means of the categories only; nay, it consists itself of the mere relation of something in general to our senses. In the same manner, it is impossible for us to represent the relations of things in abstracto as long as we deal with concepts only, in any other way than that one should be the cause of determinations in the other, this being the very concept of our understanding, with regard to relations. But as in this case we make abstraction of all intuition, a whole class of determinations, by which the manifold determines its place to each of its component parts, that is, the form of sensibility (space), disappears, though in truth [p. 286] it precedes all empirical casuality.

Section III

Of Trowing, Knowing, and Believing [p. 820]

The holding a thing to be true is an event in our understanding which, though it may rest on objective grounds, requires also subjective causes in the mind of the person who is to judge. If the judgment is valid for everybody, if only he is possessed of reason, then the ground of it is objectively sufficient, and the holding it to be true is called conviction. If, on the contrary, it has its ground in the peculiar character of the subject only, it is called persuasion.

Persuasion is a mere illusion, the ground of the judgment, though it lies solely in the subject, being regarded as objective. Such a judgment has, therefore, private validity only, and the holding it to be true cannot be communicated to others. Truth, however, depends on agreement with the object, and, with regard to it, the judgments of every understanding must agree with each other (consentientia uni tertio consentiunt inter se, etc.). An external criterion, therefore, as to whether our holding a thing to be true be conviction or only persuasion, consists in the possibility of communicating it, and finding its truth to be valid for the reason of every man. For, in that case, there is at least a presumption that the ground of the agreement of all judgments, in [p. 821] spite of the diversity of the subjects, rests upon the common ground, namely, on the object with which they all agree, and thus prove the truth of the judgment.

Persuasion, therefore, cannot be distinguished from conviction, subjectively, so long as the subject views its judgment as a phenomenon of his own mind only; the experiment, however, which we make with the grounds that seem valid to us, by trying to find out whether they will produce the same effect on the reason of others, is a means, though only a subjective means, not indeed of producing conviction, but of detecting the merely private validity of the judgment, that is, of discovering in it what is merely persuasion.

If we are able besides to analyse the subjective causes of our judgment, which we have taken for its objective grounds, and thus explain the deceptive judgment as a phenomenon in our mind, without having recourse to the object itself, we expose the illusion and are no longer deceived by it, although we may continue to be tempted by it, in a certain degree, if, namely, the subjective cause of the illusion is inherent in our nature.

I cannot maintain anything, that is, affirm it as a judgment necessarily valid for everybody, except it work conviction. Persuasion I may keep for myself, if it [p. 822] is agreeable to me, but I cannot, and ought not to attempt to make it binding on any but myself.

The holding anything to be true, or the subjective validity of a judgment admits, with reference to the conviction which is at the same time valid objectively, of the three following degrees, trowing, believing, knowing. Trowing is to hold true, with the consciousness that it is insufficient both subjectively and objectively. If the holding true is sufficient subjectively, but is held to be insufficient objectively, it is called believing; while, if it is sufficient both subjectively and objectively, it is called knowing. Subjective sufficiency is called conviction (for myself), objective sufficiency is called certainty (for everybody). I shall not dwell any longer on the explanation of such easy concepts.

I must never venture to trow, or to be of opinion, without knowing at least something by means of which a judgment, problematical by itself, is connected with truth, which connection, though it involves not a complete truth, is yet attended with more than arbitrary fiction. Moreover, the law of such a connection must be certain. For if, even with regard to this law, I should have nothing but an opinion, all would become a mere play of the imagination, without the least relation to truth.

In the judgments of pure reason opinion is not permitted. For, as they are not based on empirical grounds, but everything has to be known a priori, and [p. 823] everything therefore must be necessary, the principle of connection in them requires universality and necessity, and consequently perfect certainty, without which there would be nothing to lead us on to truth. Hence it is absurd to have an opinion in pure mathematics; here one must either know, or abstain from pronouncing any judgment. The same applies to the principles of morality, because one must not hazard an action on the mere opinion that it is allowed, but must know it to be so.

In the transcendental employment of reason, on the contrary, mere opinion, no doubt, would be too little, but knowledge too much. Speculatively, therefore, we cannot here form any judgment at all, because the subjective grounds on which we hold a thing to be true, as for instance those which may very well produce belief, are not approved of in speculative questions, as they cannot be held without empirical support, nor, if communicated to others, can produce the same effect on them.

Nor can the theoretically insufficient acceptance of truth be called belief, except from a practical point of view. And this practical view refers either to skill or to morality, the former being concerned with any contingent and casual ends and objects whatsoever, the latter with absolutely necessary ends only.

If we have once proposed an object or end to ourselves, the conditions of attaining it are hypothetically necessary. This necessity is subjective, and yet but relatively [p. 824] sufficient, if I know of no other conditions under which the end can be attained: it is sufficient absolutely and for every one, if I am convinced that no one can know of other conditions, leading to the attainment of our end. In the former case my assuming and holding certain conditions as true is merely an accidental belief, while in the latter case it is a necessary belief. Thus a physician, for instance, may feel that he must do something for a patient, who is in danger. But as he does not know the nature of the illness, he observes the symptoms, and arrives at the conclusion, as he knows nothing else, that it is phthisis. His belief, according to his own judgment, is contingent only, and he knows that another might form a better judgment. It is this kind of contingent belief which, nevertheless, supplies a ground for the actual employment of means to certain actions, which I call pragmatic belief.

The usual test, whether something that is maintained be merely persuasion, or a subjective conviction at least, that is, firm belief, is betting. People often pronounce their views with such bold and uncompromising assurance that they seem to have abandoned all fear of error. A bet startles them. Sometimes it turns out that a man has persuasion sufficient to be valued at one ducat, but not at ten; he is ready to venture the first ducat, but [p. 825] with ten, he becomes aware for the first time that, after all, it might be possible that he should be mistaken. If we imagine that we have to stake the happiness of our whole life, the triumphant air of our judgment drops considerably; we become extremely shy, and suddenly discover that our belief does not reach so far. Thus pragmatic belief admits of degrees which, according to the difference of the interests at stake, may be large or small.

Now it is true, no doubt, that, though with reference to an object of our belief, we can do nothing, and our opinion is, therefore, purely theoretical, yet in many cases we can represent and imagine to ourselves an undertaking for which we might think that we had sufficient inducements, if any means existed of ascertaining the truth of the matter. Thus, even in purely theoretical judgments, there is an analogon of practical judgments to which the word belief may be applied, and which we shall therefore call doctrinal belief. If it were possible to apply any test of experience, I should be ready to stake the whole of my earthly goods on my belief that at least one of the planets which we see is inhabited. Hence I say that it is not only an opinion, but a strong belief, on the truth of which I should risk even many advantages of life, that there are inhabitants in other worlds.

Now we must admit that the doctrine of the [p. 826] existence of God belongs to doctrinal belief. For although, with reference to my theoretical knowledge of the world, I can produce nothing which would make this thought a necessary supposition as a condition of my being able to explain the phenomena of the world, but on the contrary am bound to use my reason as if everything were mere nature, nevertheless, the unity of design is so important a condition of the application of reason to nature that I cannot ignore it, especially as experience supplies so many examples of it. Of that unity of design, however, I know no other condition, which would make it a guidance in my study of nature, but the supposition that a supreme intelligence has ordered all things according to the wisest ends. As a condition, therefore, of, it may be, a contingent, but not unimportant end, namely, in order to have a guidance in the investigation of nature, it is necessary to admit a wise author of the world. The result of my experiment confirms the usefulness of this supposition so many times, while nothing decisive can be adduced against it, that I am really saying far too little, if I call my acceptation of it a mere opinion, and it may be said, even with regard to these theoretical matters, that I firmly believe in God. Still, if we use our words strictly, this belief must always be called doctrinal, and not practical, such as the theology of nature (physical theology) must always [p. 827] and necessarily produce. In the same wisdom, and in the prominent endowments of human nature, combined with the inadequate shortness of life, another sufficient ground may be found for the doctrinal belief in the future life of the human soul.

The expression of belief is in such cases an expression of modesty from the objective point of view, and yet, at the same time, a firm confidence from a subjective. If even I were to call this purely theoretical acceptance an hypothesis only, which I am entitled to assume, I should profess to be in possession of a more complete concept of the nature of a cause of the world, and of another world, than I really can produce. If I accept anything, even as an hypothesis only, I must know it at least so much according to its properties, that I need not imagine its concepts, but its existence only. But the word belief refers only to the guidance which an idea gives me, and to its subjective influence on the conduct of my reason, which makes me hold it fast, though I may not be able to give an account of it from a speculative point of view.

Purely doctrinal belief, however, has always a somewhat unstable character. Speculative difficulties often make us lose hold of it, though in the end we always [p. 828] return to it.

It is quite different with moral belief. For here action is absolutely necessary, that is, I must obey the moral law on all points. The end is here firmly established, and, according to all we know, one only condition is possible under which that end could agree with all other ends, and thus acquire practical validity, namely, the existence of a God and of a future world. I also know it for certain that no one is cognisant of other conditions which could lead to the same unity of ends under the moral law. As, then, the moral precept is at the same time my maxim, reason commanding that it should be so, I shall inevitably believe in the existence of God, and in a future life, and I feel certain that nothing can shake this belief, because all my moral principles would be overthrown at the same time, and I cannot surrender them without becoming hateful in my own eyes.

We see, therefore, that, even after the failure of all the ambitious schemes of reason to pass beyond the limits of all experience, enough remains to make us satisfied for practical purposes. No one, no doubt, will be able to boast again that he knows that there is a God and a future life. For a man who knows that, is the very man [p. 829] whom I have been so long in search of. As all knowledge, if it refers to an object of pure reason, can be communicated, I might hope that, through his teaching, my own knowledge would be increased in the most wonderful way. No, that conviction is not a logical, but a moral certainty; and, as it rests on subjective grounds (of the moral sentiment), I must not even say that it is morally certain that there is a God, etc., but that I am morally certain, etc. What I really mean is, that the belief in a God and in another world is so interwoven with my moral sentiment, that as there is little danger of my losing the latter, there is quite as little fear lest I should ever be deprived of the former.

The only point that may rouse misgivings is that this rational belief is based on the supposition of moral sentiments. If we surrender this, and take a man who is entirely indifferent with regard to moral laws, the question proposed by reason becomes merely a problem for speculation, and may in that case be still supported with strong grounds from analogy, but not such to which the most obstinate scepticism has to submit.1

No man, however, is with regard to these questions [p. 830] free from all interest. For although in the absence of good sentiments he may be rid of all moral interest, enough remains even thus to make him fear the existence of God and a future life. For nothing is required for this but his inability to plead certainty with regard to the nonexistence of such a being and of a future life. As this would have to be proved by mere reason, and therefore apodictically, he would have to establish the impossibility of both, which I feel certain no rational being would venture to do. This would be a negative belief which, though it could not produce morality and good sentiments, would still produce something analogous, namely, a check on the outbreak of evil.

But, it will be said, is this really all that pure reason can achieve in opening prospects beyond the limits of experience? Nothing more than two articles of faith? Surely even the ordinary understanding could have achieved as much without taking counsel of [p. 831] philosophers!

I shall not here dwell on the benefits which, by the laborious efforts of its criticism, philosophy has conferred on human reason, granting even that in the end they should turn out to be merely negative. On this point something will have to be said in the next section. But I ask, do you really require that knowledge, which concerns all men, should go beyond the common understanding, and should be revealed to you by philosophers only? The very thing which you find fault with, is the best confirmation of the correctness of our previous assertions, since it reveals to us what we could not have grasped before, namely, that in matters which concern all men without distinction, nature cannot be accused of any partial distribution of her gifts; and that with regard to the essential interests of human nature, the highest philosophy can achieve no more than that guidance which nature has vouchsafed even to the meanest understanding.

Chapter III

The Architectonic of Pure Reason [p. 832]

By architectonic I understand the art of constructing systems. As systematical unity is that which raises common knowledge to the dignity of a science, that is, changes a mere aggregate of knowledge into a system, it is easy to see that architectonic is the doctrine of what is really scientific in our knowledge, and forms therefore a necessary part of the doctrine of method.

Under the sway of reason our knowledge must not remain a rhapsody, but must become a system, because thus alone can the essential objects of reason be supported and advanced. By system I mean the unity of various kinds of knowledge under one idea. This is the concept given by reason of the form of the whole, in which concept both the extent of its manifold contents and the place belonging to each part are determined a priori. This scientific concept of reason contains, therefore, the end and also the form of the whole which is congruent with it. The unity of the end to which all parts relate and through the idea of which they are related to each other, enables us to miss any part, if we possess a knowledge of the rest, and prevents any arbitrary addition or vagueness of perfection of which the limits could not be determined a priori. Thus the whole is articulated (articulatio), [p. 833] not aggregated (coacervatio). It may grow internally (per intussusceptionem), but not externally (per appositionem), like an animal body, the growth of which does not add any new member, but, without changing their proportion, renders each stronger and more efficient for its purposes.

The idea requires for its realisation a schema, that is an essential variety, and an order of its parts, which are determined a priori, according to the principles inherent in its aim. A schema, which is not designed according to an idea, that is, according to the principal aim of reason, but empirically only, in accordance with accidental aims (the number of which cannot be determined beforehand) gives technical unity; but the schema which originates from an idea only (where reason dictates the aims a priori and does not wait for them in experience) supplies architectonical unity. Now what we call a science, the schema of which must have its outline (monogramma) and the division of the whole into parts devised according to the idea, that is, a priori, and keep it perfectly distinct from everything else according to principles, cannot be produced technically according to the similarity of its various parts or the accidental use of knowledge in concreto for this or that external purpose, but architectonically only, as based on the affinity of its parts and their dependence on one supreme and internal aim through which alone the whole becomes possible. [p. 834]

No one attempts to construct a science unless he can base it on some idea; but in the elaboration of it the schema, nay, even the definition, which he gives in the beginning of his science, corresponds very seldom to his idea which, like a germ, lies hidden in reason, and all the parts of which are still enveloped and hardly distinguishable even under microscopical observation. It is necessary, therefore, to explain and determine all sciences, considering that they are contrived from the point of view of a certain general interest, not according to the description given by their author, but according to the idea which, from the natural unity of its constituent parts, we may discover as founded in reason itself. We shall often find that the originator of a science, and even his latest successors are moving vaguely round an idea which they have not been able to perceive clearly, failing in consequence to determine rightly the proper contents, the articulation (systematical unity), and the limits of their science.

It is a misfortune that only after having collected for a long time at haphazard, under the influence of an idea that lies hidden in us, materials belonging to a science, nay, after having for a long time fitted them together [p. 835] technically, a time arrives when we are able to see its idea in a clearer light, and to devise architectonically a whole system according to the aims of reason. Systems seem to develope like worms through a kind of generatio aequivoca, by the mere aggregration of numerous concepts, at first imperfect, and gradually attaining to perfection, though in reality they all had their schema, as their original germ, in reason which was itself being developed. Hence, not only is each of them articulated according to an idea, but all may be properly combined with each other in a system of human knowledge, as members of one whole, admitting of an architectonic of all human knowledge which in our time, when so much material has been collected or may be taken over from the ruins of old systems, is not only possible, but not even very difficult. We shall confine ourselves here to the completion of our proper business, namely, to sketch the architectonic of all knowledge arising from pure reason, beginning only at the point where the common root of our knowledge divides into two stems, one of which is reason. By reason, however, I understand here the whole higher faculty of knowledge, and I distinguish therein rational from empirical knowledge.

If I take no account of the contents of knowledge, objectively considered, all knowledge is, from a subjective point of view, either historical or rational. Historical [p. 836] knowledge is cognitio ex datis, rational knowledge cognitio ex principiis. Whatever may be the first origin of some branch of knowledge, it is always historical, if he who possesses it knows only so much of it as has been given to him from outside, whether through immediate experience, or through narration, or by instruction also (in general knowledge). Hence a person who, in the usual sense, has learnt a system of philosophy, for instance the Wolfian, though he may carry in his head all the principles, definitions, and proofs, as well as the division of the whole system, and have it all at his fingers’ ends, possesses yet none but a complete historical knowledge of the Wolfian philosophy. His knowledge and judgments are no more than what has been given him. If you dispute any definition, he does not know whence to take another, because he formed his own on the reason of another. But the imitative is not the productive faculty, that is, knowledge in his case did not come from reason, and though objectively it is rational knowledge, subjectively it is historical only. He has taken and kept, that is, he has well learned and has become a plaster cast of a living man. Knowledge, which is rational objectively (that is, which can arise originally from a man’s own reason only), can then only be so called subjectively also, when they have been drawn from the general resources of reason, that is, from principles from which [p. 837] also criticism, nay, even the rejection of what has been learnt, may arise.

All knowledge of reason is again either based on concepts or on the construction of concepts; the former being called philosophical, the latter mathematical. Of their essential difference I have treated in the first chapter. Knowledge, as we saw, may be objectively philosophical, and yet subjectively historical, as is the case with most apprentices, and with all who never look beyond their school and remain in a state of pupilage all their life. But it is strange that mathematical knowledge, as soon as it has been acquired, may be considered, subjectively also, as knowledge of reason, there being no such distinction here as in the case of philosophical knowledge. The reason is that the sources from which alone the mathematical teacher can take his knowledge lie nowhere but in the essential and genuine principles of reason, and cannot be taken by the pupil from anywhere else, nor ever be disputed, for the simple ground that the employment of reason takes place here in concreto only, although a priori, namely, in the pure and therefore faultless intuition, thus excluding all illusion and error. Of all the sciences of reason (a priori), therefore, mathematics alone can be learnt, but philosophy (unless it be historically) never; with regard to reason we can at most learn to philosophise.

The system of all philosophical knowledge [p. 838] is called philosophy. It must be taken objectively, if we understand by it the type of criticising all philosophical attempts, which is to serve for the criticism of every subjective philosophy, however various and changeable the systems may be. In this manner philosophy is a mere idea of a possible science which exists nowhere in concreto, but which we may try to approach on different paths, until in the end the only true path, though overgrown and hidden by sensibility, has been discovered, and the image, which has so often proved a failure, has become as like the original type as human power can ever make it. Till then we cannot learn philosophy; for where is it, who possesses it, and how shall we know it? We can only learn to philosophise, that is, to exercise the talent of reason, according to its general principles, on certain given attempts always, however, with the reservation of the right of reason of investigating the sources of these principles themselves, and of either accepting or rejecting them.

So far the concept of philosophy is only scholastic, as of a system of knowledge which is sought and valued as a science, without aiming at more than a systematical unity of that knowledge, and therefore the logical perfection of it. But there is also a universal, or, if we may say so, a cosmical concept (conceptus cosmicus) of philosophy, which always formed the real foundation of that name, [p. 839] particularly when it had, as it were, to be personified and represented in the ideal of the philosopher, as the original type. In this sense philosophy is the science of the relation of all knowledge to the essential aims of human reason (teleologia rationis humanae), and the philosopher stands before us, not as an artist, but as the lawgiver of human reason. In that sense it would be very boastful to call oneself a philosopher, and to pretend to have equalled the type which exists in the idea only.

The mathematician, the student of nature, and the logician, however far the two former may have advanced in rational, and the last, particularly, in philosophical knowledge, are merely artists of reason. There is besides, an ideal teacher, who controls them all, and uses them as instruments for the advancement of the essential aims of human reason. Him alone we ought to call philosopher: but as he exists nowhere, while the idea of his legislation exists everywhere in the reason of every human being, we shall keep entirely to that idea, and determine more accurately what kind of systematical unity philosophy, in this cosmical concept,1 demands from the standpoint of its aims. [p. 840]

Essential ends are not as yet the highest ends; in fact, there can be but one highest end, if the perfect systematical unity of reason has been reached. We must distinguish, therefore, between the ultimate end and subordinate ends, which necessarily belong, as means, to the former. The former is nothing but the whole destination of man, and the philosophy which relates to it is called moral philosophy. O account of this excellence which distinguishes moral philosophy from all other operations of reason, the ancients always understood under the name of philosopher the moralist principally: and even at present the external appearance of self-control by means of reason leads us, through a certain analogy, to call a man a philosopher, however limited his knowledge may be. The legislation of human reason (philosophy) has two objects only, nature and freedom, and contains therefore both the law of nature and the law of morals, at first in two separate systems, but combined, at last, in one great system of philosophy. The philosophy of nature relates to all that is; that of morals to that only that ought to be.

All philosophy is either knowledge derived from pure reason, or knowledge of reason derived from empirical principles. The former is called pure, the latter empirical philosophy.

The philosophy of pure reason is either propaedeutic [p. 841] (preparation), enquiring into the faculties of reason, with regard to all pure knowledge a priori, and called critic, or, secondly, the system of pure reason (science), comprehending in systematical connection the whole (both true and illusory) of philosophical knowledge, derived from pure reason, and called metaphysic, — although this name of metaphysic may be given also to the whole of pure philosophy, inclusive of the critic, in order thus to comprehend both the investigation of all that can ever be known a priori and the representation of all that constitutes a system of pure philosophical knowledge of that kind, excluding all that belongs to the empirical and the mathematical employment of reason.

Metaphysic is divided into that of the speculative and that of the practical use of pure reason, and is, therefore, either metaphysic of nature or metaphysic of morals. The former contains all the pure principles of reason, derived from concepts only (excluding therefore mathematics), of the theoretical knowledge of all things, the latter, the principles which determine a priori and necessitate all doing and not doing. Morality is the only legality of actions that can be derived from principles entirely a priori. Hence the metaphysic of morals is really pure moral philosophy, in which no account is taken of anthropology or any empirical conditions. Metaphysic of speculative [p. 842] reason has commonly been called metaphysic, in the more limited sense; as however pure moral philosophy belongs likewise to this branch of human and philosophical knowledge, derived from pure reason, we shall allow it to retain that name, although we leave it aside for the present as not belonging to our immediate object.

It is of the highest importance to isolate various sorts of knowledge, which in kind and origin are different from others, and to take great care lest they be mixed up with those others with which, for practical purposes, they are generally united. What is done by the chemist in the analysis of substances, and by the mathematician in pure mathematics, is far more incumbent on the philosopher, in order to enable him to define clearly the part which, in the promiscuous employment of the understanding, belongs to a special kind of knowledge, as well as its peculiar value and influence. Human reason, therefore, since it first began to think, or rather to reflect, has never been able to do without a metaphysic, but it has never kept it sufficiently free from all foreign admixture. The idea of a science of this kind is as old as speculation itself, and what human reason does not speculate, whether in a scholastic or a popular manner? It must be admitted, however, that even thinkers by profession did [p. 843] not clearly distinguish between the two elements of our knowledge, the one being in our possession completely apriori, the other deducible a posteriori only from experience, and did not succeed therefore in fixing the limits of a special kind of knowledge, nor in realising the true idea of a science which had so long and so deeply engaged the interest of human reason. When it was said that metaphysic is the science of the first principles of human knowledge, this did not mark out any special kind of knowledge, but only a certain rank or degree, with regard to its character of generality, which was not sufficient to distinguish it clearly from empirical knowledge. For among empirical principles also, some are more general, and therefore higher than others; and in such a series of subordinated principles (where that which is entirely a priori is not distinguished from that which is known a posteriori only), where should one draw the line to separate the first part from the last, and the higher members from the lower? What should we say if chronology should distinguish the epochs of history no better than by dividing it into the first centuries and the subsequent centuries? We should ask, no doubt, whether the fifth or the tenth belongs to the first centuries? and I ask in the same way whether the concept of what is extended belongs to metaphysic? If you say, yes! I ask, what about the concept of a body? and of a liquid body? You then hesitate, for you [p. 844] begin to see, that if I continue in this strain, everything would belong to metaphysic. It thus becomes clear that the mere degree of subordination of the special under the general cannot determine the limits of a science; but, in our case, only the complete difference in kind and origin. The fundamental idea of metaphysic was obscured on another side because, as knowledge a priori, it showed a certain similarity in kind with mathematics. The two are, no doubt, related with regard to their origin a priori, but, if we consider how, in metaphysic, knowledge is derived from concepts, while in mathematics we can only form judgments through the construction of concepts a priori, we discover, in comparing philosophical with mathematical knowledge, the most decided difference in kind, which was no doubt always felt, but never determined by clear criteria. Thus it has happened that, as philosophers themselves blundered in developing the idea of their science, its elaboration could have no definite aim, and no certain guidance; and we may well understand how metaphysical science was brought into contempt in the outside world, and at last among philosophers themselves, considering how arbitrarily it had been designed, and how constantly those very philosophers, ignorant as to the path which they ought to take, were disputing among themselves about the discoveries which each asserted he had made on his own peculiar path. [p. 845]

All pure knowledge a priori constitutes, therefore, according to the special faculty of knowledge in which alone it can originate, a definite unity; and metaphysic is that philosophy which is meant to represent that knowledge in its systematical unity. Its speculative part, which has especially appropriated that name, namely, what we call metaphysic of nature, in which everything is considered from concepts a priori, so far as it is (not so far as it ought to be), will have to be divided in the following manner.

Metaphysic, in the more limited sense of the word, consists of transcendental philosophy and the physiology of pure reason. The former treats only of understanding and reason themselves, in a system of all concepts and principles which have reference to objects in general, without taking account of objects that may be given (ontologia): the latter treats of nature, that is, the sum of given objects (whether given to the senses, or, if you like, to some other kind of intuition) and is therefore physiology, although rationalis only. The employment of reason in this rational study of nature is either physical or hyperphysical, or, more accurately speaking, immanent or transcendent. The former refers to nature, in so far as its knowledge can take place in experience (in concreto); the latter to that connection of objects of experience which transcends all experience. This transcendent physiology has for its object either an [p. 846] internal or an external connection, both transcending every possible experience; the former is the physiology of nature as a whole, or transcendental knowledge of the world, the latter refers to the connection of the whole of nature with a Being above nature, and is therefore transcendental knowledge of God.

Immanent physiology, on the contrary, considers nature as the sum total of all objects of the senses, such, therefore, as it is given us, but only according to conditions a priori, under which alone it can be given us. It has two kinds of objects only; first, those of the external senses, which constitute together corporeal nature; secondly, the object of the internal sense, the soul, and what, according to its fundamental principles in general, may be called thinking nature. The metaphysic of corporeal nature is called physic, or, because it must contain the principles of an a priori knowledge of nature only, rational physic. Metaphysic of the thinking nature is called psychology, and for the same reason, is here to be understood as the rational knowledge only of that nature.

Thus the whole system of metaphysic consists of four principal parts. 1. Ontology, 2. Rational Physiology, 3. Rational Cosmology, 4. Rational Theology. The second part, the physiology of pure reason, contains two divisions, namely, physica rationalis,1 and phychologia [p. 847] rationalis.

The fundamental idea of a philosophy of pure reason prescribes itself this division. It is therefore architectonical, adequate to its essential aims, and not technical only, contrived according to any observed similarities, and, as it were, at haphazard. For that very reason such a division is unchangeable and of legislative authority. There are, however, a few points which might cause misgivings, and weaken our conviction of its legitimate character.

First of all, how can I expect knowledge a priori, that is metaphysic, of objects so far as they are given to our senses, that is a posteriori? and how is it possible to know the nature of things according to principles a priori, and thus to arrive at a rational physiology? Our [p. 848] answer is, that we take nothing from experience beyond what is necessary to give us an object, either of the external or of the internal sense. The former is done by the mere concept of matter (impermeable, lifeless extension), the latter through the concept of a thinking being (in the empirical internal representation, I think). For the rest, we ought in the whole metaphysical treatment of these objects to abstain from all empirical principles, which to the concept of matter might add any kind of experience for the purpose of forming any judgments on these objects.

Secondly. What becomes of empirical psychology, which has always maintained its place in metaphysic and from which, in our time, such great things were expected for throwing light on metaphysic, after all hope had been surrendered of achieving anything useful a priori? I answer, it has its place where the proper (empirical) study of nature must be placed, namely, by the side of applied philosophy, to which pure philosophy supplies the principles a priori; thus being connected, but not to be confounded with it. Empirical psychology, therefore, must be entirely banished from metaphysic, and is excluded from it by its very idea. According to the tradition of the schools, however, we shall probably have to allow to it (though as an episode only) a small corner in metaphysic, and this [p. 849] from economical motives, because, as yet, it is not so rich as to constitute a study by itself, and yet too important to be banished entirely and to be settled in a place where it would find still less affinity than in metaphysic. It is, therefore, a stranger only, who has been received for a long time and whom one allows to stay a little longer, until he can take up his own abode in a complete system of anthropology, the pendant to the empirical doctrine of nature.

This then is the general idea of metaphysic which, as in the beginning more was expected of it than could justly be demanded, fell into general disrepute after these pleasant expectations had proved fallacious. The whole course of our critique must have convinced us sufficiently that, although metaphysic cannot supply the foundation of religion, it must always remain its bulwark, and that human reason, being dialectical by its very nature, cannot do without a science which curbs it and, by means of a scientific and perfectly clear self-knowledge, prevents the ravages which otherwise this lawless speculative reason would certainly commit both in morals and religion. We may be sure, therefore, that, in spite of the coy or contemptuous airs assumed by those who judge a science, not according to its nature, but according to its accidental [p. 850] effects, we shall always return to it as to a beloved one with whom we have quarrelled, because reason, as essential interests are here at stake, cannot rest till it has either established correct views or destroyed those which already exist.

Metaphysic, therefore, that of nature as well as that of morals, and particularly the criticism of our adventurous reason, which forms the introduction and preparation of it, constitute together what may be termed philosophy in the true sense of the word. Its only goal is wisdom, and the path to it science, the only path which, if once opened, is never grown over again, and can never mislead. Mathematics, natural science, even the empirical knowledge of men, have, no doubt, a high value, as means for the most part to accidental, but yet in the end necessary and essential aims of mankind. But they have that value only by means of that knowledge of reason based on pure concepts which, call it as you may, is in reality nothing but metaphysic.

For the same reason metaphysic is also the completion of the whole culture of human reason, which is indispensable, although one may discard its influence as a science with regard to certain objects. For it enquires [p. 851] into reason according to its elements and highest maxims, which must form the very foundation of the possibility of some sciences, and of the use of all. That, as mere speculation, it serves rather to keep off error than to extend knowledge does not detract from its value, but, on the contrary, confers upon it dignity and authority by that censorship which secures general order and harmony, ay, the well-being of the scientific commonwealth, and prevents its persevering and successful labourers from losing sight of the highest aim, the general happiness of all mankind.

Chapter IV

The History of Pure Reason [p. 852]

This title stands here only in order to indicate the place in the system which remains empty for the present and has to be filled hereafter. I content myself with casting a cursory glance, from a purely transcendental point of view, namely, that of the nature of pure reason, on the labours of former philosophers, which presents to my eyes many structures, but in ruins only.

It is very remarkable, though naturally it could not well have been otherwise, that in the very infancy of philosophy men began where we should like to end, namely, with studying the knowledge of God and the hope or even the nature of a future world. However crude the religious concepts might be which owed their origin to the old customs, as remnants of the savage state of humanity, this did not prevent the more enlightened classes from devoting themselves to free investigations of these matters, and they soon perceived that there could be no better and surer way of pleasing that invisible power which governs the world, in order to be happy at least in another world, than good conduct. Thus theology and morals [p. 853] became the two springs, or rather the points of attraction for all abstract enquiries of reason in later times, though it was chiefly the former which gradually drew speculative reason into those labours which afterwards became so celebrated under the name of metaphysic.

I shall not attempt at present to distinguish the periods of history in which this or that change of metaphysic took place, but only draw a rapid sketch of the difference of the ideas which caused the principal revolutions in metaphysic. And here I find three aims with which the most important changes on this arena were brought about.

1. With reference to the object of all knowledge of our reason, some philosophers were mere sensualists, others mere intellectualists. Epicurus may be regarded as the first among the former, Plato as the first among the latter. The distinction of these two schools, subtle as it is, dates from the earliest days, and has long been maintained. Those who belong to the former school maintained that reality exists in the objects of the senses alone, everything else being imagination; those of the second school, on the contrary, maintained, that in the senses there is nothing but illusion, and that the true is known by the [p. 854] understanding only. The former did not, therefore, deny all reality to the concepts of the understanding, but that reality was with them logical only, with the others it was mystical. The former admitted intellectual concepts, but accepted sensible objects only. The latter required that true objects should be intelligible only, and maintained an intuition peculiar to the understanding, separated from the senses which, in their opinion, could only confuse it.

2. With reference to the origin of the pure concepts of reason, and whether they are derived from experience, or have their origin independent of experience, in reason. Aristotle may be considered as the head of the empiricists,Plato as that of the noologists. Locke, who in modern times followed Aristotle, and Leibniz, who followed Plato (though at a sufficient distance from his mystical system), have not been able to bring this dispute to any conclusion. Epicurus at least was far more consistent in his sensual system (for he never allowed his syllogisms to go beyond the limits of experience) than Aristotle and Locke, more particularly the latter, who, after having derived all concepts and principles from experience, goes so far in their application as to maintain that the existence of God and the immortality of the soul (though both lie entirely outside the limits of all possible experience) could [p. 855] be proved with the same evidence as any mathematical proposition.

3. With reference to method. If anything is to be called method, it must be a procedure according to principles. The method at present prevailing in this field of enquiry may be divided into the naturalistic and the scientific. The naturalist of pure reason lays it down as his principle that, with reference to the highest questions which form the problems of metaphysic, more can be achieved by means of common reason without science (which he calls sound reason), than through speculation. This is the same as if we should maintain that the magnitude and distance of the moon can be better determined by the naked eye than by roundabout mathematical calculations. This is pure misology reduced to principles, and, what is the most absurd, the neglect of all artificial means is recommended as the best way of enlarging our knowledge. As regards those who are naturalists because they know no better, they are really not to be blamed. They simply follow ordinary reason, but they do not boast of their ignorance, as the method which contains the secret how we are to fetch the truth from the bottom of the well of Democritus. ‘Quod sapio satis est mihi, non ego curo, esse quod Arcesilas aerumnosique Solones’ (Pers.), is the motto with which they may lead a happy and honoured life, without meddling with science or muddling it. [p. 856]

As regards those who follow a scientific method, they have the choice to proceed either dogmatically or sceptically, but at all events, systematically. When I have mentioned in relation to the former the celebrated Wolf, and in relation to the other David Hume, I may for my present purpose leave all the rest unnamed.

The only path that is still open is the critical. If the reader has been kind and patient enough to follow me to the end along this path, he may judge for himself whether, if he will help, as far as in him lies, towards making this footpath a highroad, it may not be possible to achieve, even before the close of the present century, what so many centuries have not been able to achieve, namely, to give complete satisfaction to human reason with regard to those questions which have in all ages exercised its desire for knowledge, though hitherto in vain.

SUPPLEMENT I

MOTTO TO SECOND EDITION

Baco de Verulamio

Instauratio magna: Praefatio

De nobis ipsis silemus: de re autem, quae agitur, petimus, ut homines eam non opinionem, sed opus esse cogitent; ac pro certo habeant, non sectae nos alicujus aut placiti, sed utilitatis et amplitudinis humanae fundamenta moliri. Deinde ut suis commodis aequi . . . in commune consulant, . . . et ipsi in partem veniant. Praeterea, ut bene sperent, neque Instaurationem nostram ut quiddam infinitum et ultra mortale fingant, et animo concipiant; quum revera sit infiniti erroris finis et terminus legitimus.

SUPPLEMENT II

Preface to the Second Edition. 1787. [p. vii]

Whether the treatment of that class of knowledge with which reason is occupied follows the secure method of a science or not, can easily be determined by the result. If, after repeated preparations, it comes to a standstill, as soon as its real goal is approached, or is obliged, in order to reach it, to retrace its steps again and again, and strike into fresh paths; again, if it is impossible to produce unanimity among those who are engaged in the same work, as to the manner in which their common object should be obtained, we may be convinced that such a study is far from having attained to the secure method of a science, but is groping only in the dark. In that case we are conferring a great benefit on reason, if we only find out the right method, though many things should have to be surrendered as useless, which were comprehended in the original aim that had been chosen without sufficient reflection.

That Logic, from the earliest times, has followed that [p. viii] secure method, may be seen from the fact that since Aristotle it has not had to retrace a single step, unless we choose to consider as improvements the removal of some unnecessary subtleties, or the clearer definition of its matter, both of which refer to the elegance rather than to the solidity of the science. It is remarkable also, that to the present day, it has not been able to make one step in advance, so that, to all appearance, it may be considered as completed and perfect. If some modern philosophers thought to enlarge it, by introducing psychological chapters on the different faculties of knowledge (faculty of imagination, wit, etc.), or metaphysical chapters on the origin of knowledge, or the different degrees of certainty according to the difference of objects (idealism, scepticism, etc.), or lastly, anthropological chapters on prejudices, their causes and remedies, this could only arise from their ignorance of the peculiar nature of logical science. We do not enlarge, but we only disfigure the sciences, if we allow their respective limits to be confounded: and the limits of logic are definitely fixed by the fact, that it is a science which has nothing to do but fully to exhibit and strictly to prove all formal [p. ix] rules of thought (whether it be a priori or empirical, whatever be its origin or its object, and whatever be the impediments, accidental or natural, which it has to encounter in the human mind).

That logic should in this respect have been so successful, is due entirely to its limitation, whereby it has not only the right, but the duty, to make abstraction of all the objects of knowledge and their differences, so that the understanding has to deal with nothing beyond itself and its own forms. It was, of course, far more difficult for reason to enter on the secure method of science, when it has to deal not with itself only, but also with objects. Logic, therefore, as a kind of preparation (propaedeutic) forms, as it were, the vestibule of the sciences only, and where real knowledge is concerned, is presupposed for critical purposes only, while the acquisition of knowledge must be sought for in the sciences themselves, properly and objectively so called.

If there is to be in those sciences an element of reason, something in them must be known a priori, and knowledge may stand in a twofold relation to its object, by either simply determining [p. x] it and its concept (which must be supplied from elsewhere), or by making it real also. The former is theoretical, the latter practical knowledge of reason. In both the pure part, namely, that in which reason determines its object entirely a priori (whether it contain much or little), must be treated first, without mixing up with it what comes from other sources; for it is bad economy to spend blindly whatever comes in, and not to be able to determine, when there is a stoppage, which part of the income can bear the expenditure, and where reductions must be made.

Mathematics and physics are the two theoretical sciences of reason, which have to determine their objects a priori; the former quite purely, the latter partially so, and partially from other sources of knowledge besides reason.

Mathematics, from the earliest times to which the history of human reason can reach, has followed, among that wonderful people of the Greeks, the safe way of a science. But it must not be supposed that it was as easy for mathematics as for logic, in which reason is concerned with itself alone, to find, or rather to make for itself that royal road. I believe, on the contrary, that there was a long period of tentative work (chiefly [p. xi] still among the Egyptians), and that the change is to be ascribed to a revolution, produced by the happy thought of a single man, whose experiment pointed unmistakably to the path that had to be followed, and opened and traced out for the most distant times the safe way of a science. The history of that intellectual revolution, which was far more important than the discovery of the passage round the celebrated Cape of Good Hope, and the name of its fortunate author, have not been preserved to us. But the story preserved by Diogenes Laertius, who names the reputed author of the smallest elements of ordinary geometrical demonstration, even of such as, according to general opinion, do not require to be proved, shows, at all events, that the memory of the revolution, produced by the very first traces of the discovery of a new method, appeared extremely important to the mathematicians, and thus remained unforgotten. A new light flashed on the first man who demonstrated the properties of the isosceles triangle1 (whether his name was Thales or any other name), for he found that he had not to investigate what [p. xii] he saw in the figure, or the mere concept of that figure, and thus to learn its properties; but that he had to produce (by construction) what he had himself, according to concepts a priori, placed into that figure and represented in it, so that, in order to know anything with certainty a priori, he must not attribute to that figure anything beyond what necessarily follows from what he has himself placed into it, in accordance with the concept.

It took a much longer time before physics entered on the high way of science: for no more than a century and a half has elapsed, since Bacon’s ingenious proposal partly initiated that discovery, partly, as others were already on the right track, gave a new impetus to it, — a discovery which, like the former, can only be explained by a rapid intellectual revolution. In what I have to say, I shall confine myself to natural science, so far as it is founded on empirical principles.

When Galilei let balls of a particular weight, which he had determined himself, roll down an inclined plain, or Torricelli made the air carry a weight, which he had previously determined to be equal to that of a definite volume of water; or when, in later times, Stahl1 changed metal into lime, and lime again into metals, by withdrawing and restoring something, a new [p. xiii] light flashed on all students of nature. They comprehended that reason has insight into that only, which she herself produces on her own plan, and that she must move forward with the principles of her judgments, according to fixed law, and compel nature to answer her questions, but not let herself be led by nature, as it were in leading strings, because otherwise accidental observations, made on no previously fixed plan, will never converge towards a necessary law, which is the only thing that reason seeks and requires. Reason, holding in one hand its principles, according to which concordant phenomena alone can be admitted as laws of nature, and in the other hand the experiment, which it has devised according to those principles, must approach nature, in order to be taught by it: but not in the character of a pupil, who agrees to everything the master likes, but as an appointed judge, who compels the witnesses to answer the questions which he himself proposes. Therefore even the science of physics entirely owes the beneficial revolution in its character to the happy thought, that we ought to seek in nature (and not [p. xiv] import into it by means of fiction) whatever reason must learn from nature, and could not know by itself, and that we must do this in accordance with what reason itself has originally placed into nature. Thus only has the study of nature entered on the secure method of a science, after having for many centuries done nothing but grope in the dark.

Metaphysic, a completely isolated and speculative science of reason, which declines all teaching of experience, and rests on concepts only (not on their application to intuition, as mathematics), in which reason therefore is meant to be her own pupil, has hitherto not been so fortunate as to enter on the secure path of a science, although it is older than all other sciences, and would remain, even if all the rest were swallowed up in the abyss of an all-destroying barbarism. In metaphysic, reason, even if it tries only to understand a priori (as it pretends to do) those laws which are confirmed by the commonest experience, is constantly brought to a standstill, and we are obliged again and again to retrace our steps, because they do not lead us where we want to go; while as to any unanimity among those who are engaged [p. xv] in the same work, there is so little of it in metaphysic, that it has rather become an arena, specially destined, it would seem, for those who wish to exercise themselves in mock fights, and where no combatant has, as yet, succeeded in gaining an inch of ground that he could call permanently his own. It cannot be denied, therefore, that the method of metaphysic has hitherto consisted in groping only, and, what is the worst, in groping among mere concepts.

What then can be the cause that hitherto no secure method of science has been discovered? Shall we say that it is impossible? Then why should nature have visited our reason with restless aspiration to look for it, as if it were its most important concern? Nay more, how little should we be justified in trusting our reason if, with regard to one of the most important objects we wish to know, it not only abandons us, but lures us on by vain hopes, and in the end betrays us! Or, if hitherto we have only failed to meet with the right path, what indications are there to make us hope that, if we renew our researches, we shall be more successful than others before us?

The examples of mathematics and natural science, which by one revolution have become what they now are, seem [p. xvi] to me sufficiently remarkable to induce us to consider, what may have been the essential element in that intellectual revolution which has proved so beneficial to them, and to make the experiment, at least, so far as the analogy between them, as sciences of reason, with metaphysic allows it, of imitating them. Hitherto it has been supposed that all our knowledge must conform to the objects: but, under that supposition, all attempts to establish anything about them a priori, by means of concepts, and thus to enlarge our knowledge, have come to nothing. The experiment therefore ought to be made, whether we should not succeed better with the problems of metaphysic, by assuming that the objects must conform to our mode of cognition, for this would better agree with the demanded possibility of an a priori knowledge of them, which is to settle something about objects, before they are given us. We have here the same case as with the first thought of Copernicus, who, not being able to get on in the explanation of the movements of the heavenly bodies, as long as he assumed that all the stars turned round the spectator, tried, whether he could not succeed better, by assuming the spectator to be turning round, and the stars to be at rest. A similar experiment may be tried in metaphysic, so far as the intuition of objects is [p. xvii] concerned. If the intuition had to conform to the constitution of objects, I do not see how we could know anything of it a priori; but if the object (as an object of the senses) conforms to the constitution of our faculty of intuition, I can very well conceive such a possibility. As, however, I cannot rest in these intuitions, if they are to become knowledge, but have to refer them, as representations, to something as their object, and must determine that object by them, I have the choice of admitting, either that the concepts, by which I carry out that determination, conform to the object, being then again in the same perplexity on account of the manner how I can know anything about it a priori; or that the objects, or what is the same, the experience in which alone they are known (as given objects), must conform to those concepts. In the latter case, the solution becomes more easy, because experience, as a kind of knowledge, requires understanding, and I must therefore, even before objects are given to me, presuppose the rules of the understanding as existing within me a priori, these rules being expressed in concepts a priori, to which all objects of experience must necessarily conform, and with which they must agree. With regard to objects, [p. xviii] so far as they are conceived by reason only, and conceived as necessary, and which can never be given in experience, at least in that form in which they are conceived by reason, we shall find that the attempts at conceiving them (for they must admit of being conceived) will furnish afterwards an excellent test of our new method of thought, according to which we do not know of things anything a priori except what we ourselves put into them.1

This experiment succeeds as well as we could desire, and promises to metaphysic, in its first part, which deals with concepts a priori, of which the corresponding objects may be given in experience, the secure method of a science. For by [p. xix] thus changing our point of view, the possibility of knowledge a priori can well be explained, and, what is still more, the laws which a priori lie at the foundation of nature, as the sum total of the objects of experience, may be supplied with satisfactory proofs, neither of which was possible with the procedure hitherto adopted. But there arises from this deduction of our faculty of knowing a priori, as given in the first part of metaphysic, a somewhat startling result, apparently most detrimental to the objects of metaphysic that have to be treated in the second part, namely, the impossibility of going with it beyond the frontier of possible experience, which is precisely the most essential purpose [p. xx] of metaphysical science. But here we have exactly the experiment which, by disproving the opposite, establishes the truth of our first estimate of the knowledge of reason a priori, namely, that it can refer to phenomena only, but must leave the thing by itself as unknown to us, though as existing by itself. For that which impels us by necessity to go beyond the limits of experience and of all phenomena, is the unconditioned, which reason postulates in all things by themselves, by necessity and by right, for everything conditioned, so that the series of conditions should thus become complete. If then we find that, under the supposition of our experience conforming to the objects as things by themselves, it is impossible to conceive the unconditioned without contradiction, while, under the supposition of our representation of things, as they are given to us, not conforming to them as things by themselves, but, on the contrary, of the objects conforming to our mode of representation, that contradiction vanishes, and that therefore the unconditioned must not be looked for in things, so far as we know them (so far as they are given to us), but only so far as we do not know them (as things by themselves), we clearly perceive that, what we at first assumed tentatively only, is fully confirmed.1 But, after all [p. xxi] progress in the field of the supersensuous has thus been denied to speculative reason, it is still open to us to see, whether in the practical knowledge of reason data may not be found which enable us to determine that transcendent concept of the unconditioned which is demanded by reason, in order thus, according to the wish of metaphysic, to get beyond the limits of all possible experience, by means of our knowledge a priori, which is possible to us for practical purposes only. In this case, speculative reason has at least gained for us room for such an extension of knowledge, though it had to leave it empty, so that we are not only at liberty, but are really called upon to fill it up, if we are able, by practical data of reason.1 [p. xxii]

The very object of the critique of pure speculative reason consists in this attempt at changing the old procedure of metaphysic, and imparting to it the secure method of a science, after having completely revolutionised it, following the example of geometry and physical science. That critique is a treatise on the method (Traité de la méthode), not a system of the science itself; but it marks out nevertheless the whole plan of that science, both with regard to its limits, and to its internal organisation. For pure speculative reason has this peculiar [p. xxiii] advantage that it is able, nay, bound to measure its own powers, according to the different ways in which it chooses its own objects, and to completely enumerate the different ways of choosing problems; thus tracing a complete outline of a system of metaphysic. This is due to the fact that, with regard to the first point, nothing can be attributed to objects in knowledge a priori, except what the thinking subject takes from within itself; while, with regard to the second point, reason, so far as its principles of cognition are concerned, forms a separate and independent unity, in which, as in an organic body, every member exists for the sake of all others, and all others exist for the sake of the one, so that no principle can be safely applied in one relation, unless it has been carefully examined in all its relations, to the whole employment of pure reason. Hence, too, metaphysic has this singular advantage, an advantage which cannot be shared by any other science, in which reason has to deal with objects (for Logic deals only with the form of thought in general) that, if it has once attained, by means of this critique, to the secure method of a science, it can completely comprehend the whole field of knowledge [p. xxiv] pertaining to it, and thus finish its work and leave it to posterity, as a capital that can never be added to, because it has only to deal with principles and the limits of their employment, which are fixed by those principles themselves. And this completeness becomes indeed an obligation, if it is to be a fundamental science, of which we must be able to say, ‘nil actum reputans, si quid superesset agendum.’

But it will be asked, what kind of treasure is it which we mean to bequeath to posterity in this metaphysic of ours, after it has been purified by criticism, and thereby brought to a permanent condition? After a superficial view of this work, it may seem that its advantage is negative only, warning us against venturing with speculative reason beyond the limits of experience. Such is no doubt its primary use: but it becomes positive, when we perceive that the principles with which speculative reason ventures beyond its limits, lead inevitably, not to an extension, but, if carefully considered, to a narrowing of the employment of reason, because, by indefinitely extending the limits of sensibility, to which [p. xxv] they properly belong, they threaten entirely to supplant the pure (practical) employment of reason. Hence our critique, by limiting sensibility to its proper sphere, is no doubt negative; but by thus removing an impediment, which threatened to narrow, or even entirely to destroy its practical employment, it is in reality of positive, and of very important use, if only we are convinced that there is an absolutely necessary practical use of pure reason (the moral use), in which reason must inevitably go beyond the limits of sensibility, and though not requiring for this purpose the assistance of speculative reason, must at all events be assured against its opposition, lest it be brought in conflict with itself. To deny that this service, which is rendered by criticism, is a positive advantage, would be the same as to deny that the police confers upon us any positive advantage, its principal occupation being to prevent violence, which citizens have to apprehend from citizens, so that each may pursue his vocation in peace and security. We had established in the analytical part of our critique the following points: — First, that space and time are only forms of sensuous intuition, therefore conditions of the existence of things, as phenomena only; Secondly, that we have no concepts of the understanding, and therefore nothing whereby we can arrive at the knowledge of things, except in so far as an intuition [p. xxvi] corresponding to these concepts can be given, and consequently that we cannot have knowledge of any object, as a thing by itself, but only in so far as it is an object of sensuous intuition, that is, a phenomenon. This proves no doubt that all speculative knowledge of reason is limited to objects of experience; but it should be carefully borne in mind, that this leaves it perfectly open to us, to think the same objects as things by themselves, though we cannot know them.1 For otherwise we should arrive at the absurd conclusion, that there is phenomenal appearance without [p. xxvii] something that appears. Let us suppose that the necessary distinction, established in our critique, between things as objects of experience and the same things by themselves, had not been made. In that case, the principle of causality, and with it the mechanism of nature, as determined by it, would apply to all things in general, as efficient causes. I should then not be able to say of one and the same being, for instance the human soul, that its will is free, and, at the same time, subject to the necessity of nature, that is, not free, without involving myself in a palpable contradiction: and this because I had taken the soul, in both propositions, in one and the same sense, namely, as a thing in general (as something by itself), as, without previous criticism, I could not but take it. If, however, our criticism was true, in teaching us to take an object in two senses, namely, either as a phenomenon, or as a thing by itself, and if the deduction of our concepts of the understanding was correct, and the principle of causality applies to things only, if taken in the first sense, namely, so far as they are objects of experience, but not to things, if taken in their second sense, we can, without any contradiction, think the same will when phenomenal (in visible actions) as necessarily [p. xxviii] conforming to the law of nature, and so far, not free, and yet, on the other hand, when belonging to a thing by itself, as not subject to that law of nature, and therefore free. Now it is quite true that I may not know my soul, as a thing by itself, by means of speculative reason (still less through empirical observation), and consequently may not know freedom either, as the quality of a being to which I attribute effects in the world of sense, because, in order to do this, I should have to know such a being as determined in its existence, and yet as not determined in time (which, as I cannot provide my concept with any intuition, is impossible). This, however, does not prevent me from thinking freedom; that is, my representation of it contains at least no contradiction within itself, if only our critical distinction of the two modes of representation (the sensible and the intelligible), and the consequent limitation of the concepts of the pure understanding, and of the principles based on them, has been properly carried out. If, then, morality necessarily presupposed freedom (in the strictest sense) as a property of our will, producing, as a priori data of it, practical principles, belonging originally to our reason, which, without freedom, would be absolutely impossible, while speculative reason had proved that such a freedom cannot even [p. xxix] be thought, the former supposition, namely, the moral one, would necessarily have to yield to another, the opposite of which involves a palpable contradiction, so that freedom, and with it morality (for its opposite contains no contradiction, unless freedom is presupposed), would have to make room for the mechanism of nature. Now, however, as morality requires nothing but that freedom should only not contradict itself, and that, though unable to understand, we should at least be able to think it, there being no reason why freedom should interfere with the natural mechanism of the same act (if only taken in a different sense), the doctrine of morality may well hold its place, and the doctrine of nature may hold its place too, which would have been impossible, if our critique had not previously taught us our inevitable ignorance with regard to things by themselves, and limited everything, which we are able to know theoretically, to mere phenomena. The same discussion as to the positive advantage to be derived from the critical principles of pure reason might be repeated with regard to the concept of God, and of the simple nature of our soul; but, for the sake of brevity, I shall pass this by. I am not allowed therefore even to assume, for the sake [p. xxx] of the necessary practical employment of my reason, God, freedom, and immortality, if I cannot deprive speculative reason of its pretensions to transcendent insights, because reason, in order to arrive at these, must use principles which are intended originally for objects of possible experience only, and which, if in spite of this, they are applied to what cannot be an object of experience, really changes this into a phenomenon, thus rendering all practical extension of pure reason impossible. I had therefore to remove knowledge, in order to make room for belief. For the dogmatism of metaphysic, that is, the presumption that it is possible to achieve anything in metaphysic without a previous criticism of pure reason, is the source of all that unbelief, which is always very dogmatical, and wars against all morality.

If, then, it may not be too difficult to leave a bequest to posterity, in the shape of a systematical metaphysic, carried out according to the critique of pure reason, such a bequest is not to be considered therefore as of little value, whether we regard the improvement which reason receives through the secure method of a science, in place of its groundless groping and uncritical vagaries, or whether we look to the better employment [p. xxxi] of the time of our enquiring youth, who, if brought up in the ordinary dogmatism, are early encouraged to indulge in easy speculations on things of which they know nothing, and of which they, as little as anybody else, will ever understand anything; neglecting the acquirement of sound knowledge, while bent on the discovery of new metaphysical thoughts and opinions. The greatest benefit however will be, that such a work will enable us to put an end for ever to all objections to morality and religion, according to the Socratic method, namely, by the clearest proof of the ignorance of our opponents. Some kind of metaphysic has always existed, and will always exist, and with it a dialectic of pure reason, as being natural to it. It is therefore the first and most important task of philosophy to deprive metaphysic, once for all, of its pernicious influence, by closing up the sources of its errors.

In spite of these important changes in the whole field of science, and of the losses which speculative reason must suffer in its fancied possessions, all general human interests, and all the [p. xxxii] advantages which the world hitherto derived from the teachings of pure reason, remain just the same as before. The loss, if any, affects only the monopoly of the schools, and by no means the interests of humanity. I appeal to the staunchest dogmatist, whether the proof of the continued existence of our soul after death, derived from the simplicity of the substance, or that of the freedom of the will, as opposed to the general mechanism of nature, derived from the subtle, but inefficient, distinction between subjective and objective practical necessity, or that of the existence of God, derived from the concept of an Ens realissimum (the contingency of the changeable, and the necessity of a prime mover), have ever, after they had been started by the schools, penetrated the public mind, or exercised the slightest influence on its convictions? If this has not been, and in fact could not be so, on account of the unfitness of the ordinary understanding for such subtle speculations; and if, on the contrary, with regard to the first point, the hope of a future life has chiefly rested on that peculiar character of human nature, never to be satisfied by what is merely temporal (and insufficient, therefore, for the character of its whole destination); if with regard to the second, the clear consciousness of freedom was produced only by the [p. xxxiii] clear exhibition of duties in opposition to all the claims of sensuous desires; and if, lastly, with regard to the third, the belief in a great and wise Author of the world has been supported entirely by the wonderful beauty, order, and providence, everywhere displayed in nature, then this possession remains not only undisturbed, but acquires even greater authority, because the schools have now been taught, not to claim for themselves any higher or fuller insight on a point which concerns general human interests, than what is equally within the reach of the great mass of men, and to confine themselves to the elaboration of these universally comprehensible, and, for moral purposes, quite sufficient proofs. The change therefore affects the arrogant pretensions of the schools only, which would fain be considered as the only judges and depositaries of such truth (as they are, no doubt, with regard to many other subjects), allowing to the public its use only, and trying to keep the key to themselves, quod mecum nescit, solus vult scire videri. At the same time full satisfaction is given to the more moderate claims of speculative philosophers. [p. xxxiv] They still remain the exclusive depositors of a science which benefits the masses without their knowing it, namely, the critique of reason. That critique can never become popular, nor does it need to be so, because, if on the one side the public has no understanding for the fine-drawn arguments in support of useful truths, it is not troubled on the other by the equally subtle objections. It is different with the schools which, in the same way as every man who has once risen to the height of speculation, must know both the pro’s and the con’s and are bound, by means of a careful investigation of the rights of speculative reason, to prevent, once for all, the scandal which, sooner or later, is sure to be caused even to the masses, by the quarrels in which metaphysicians (and as such, theologians also) become involved, if ignorant of our critique, and by which their doctrine becomes in the end entirely perverted. Thus, and thus alone, can the very root be cut off of materialism, fatalism, atheism, free-thinking, unbelief, fanaticism, and superstition, which may become universally injurious, and finally of idealism and scepticism, also, which are dangerous rather to the schools, and can scarcely ever penetrate into the public. If [p. xxxv] governments think proper ever to interfere with the affairs of the learned, it would be far more consistent with their wise regard for science as well as for society, to favour the freedom of such a criticism by which alone the labours of reason can be established on a firm footing, than to support the ridiculous despotism of the schools, which raise a loud clamour of public danger, whenever the cobwebs are swept away of which the public has never taken the slightest notice, and the loss of which it can therefore never perceive.

Our critique is not opposed to the dogmatical procedure of reason, as a science of pure knowledge (for this must always be dogmatical, that is, derive its proof from sure principles a priori), but to dogmatism only, that is, to the presumption that it is possible to make any progress with pure (philosophical) knowledge, consisting of concepts, and guided by principles, such as reason has long been in the habit of employing, without first enquiring in what way, and by what right, it has come possessed of them. Dogmatism is therefore the dogmatical procedure of pure reason, without a previous criticism of its own powers; and our opposition to this is not intended to defend either that loquacious [p. xxxvi] shallowness which arrogates to itself the good name of popularity, much less that scepticism which makes short work with the whole of metaphysic. On the contrary, our critique is meant to form a necessary preparation in support of a thoroughly scientific system of metaphysic, which must necessarily be carried out dogmatically and strictly systematically, so as to satisfy all the demands, not so much of the public at large, as of the schools, this being an indispensable condition, as it has undertaken to carry out its work entirely a priori, and thus to the complete satisfaction of speculative reason. In the execution of this plan, as traced out by the critique, that is, in a future system of metaphysic, we shall have to follow in the strict method of the celebrated Wolf, the greatest of all dogmatic philosophers, who first showed (and by his example called forth, in Germany, that spirit of thoroughness, which is not yet extinct) how the secure method of a science could be attained only by a legitimate establishment of principles, a clear definition of concepts, an attempt at strictness of proof, and an avoidance of all bold combinations in concluding. He was therefore most eminently qualified to raise metaphysics to the dignity of a science, if it had only occurred to him, by criticism of the organum, namely, of pure reason itself, first to prepare his field, — an omission to be ascribed, not so much to himself as to the dogmatical [p. xxxvii] spirit of his age, and with regard to which the philosophers of his own, as well as of all previous times, have no right to reproach each other. Those who reject, at the same time, the method of Wolf, and the procedure of the critique of pure reason, can have no other aim but to shake off the fetters of science altogether, and thus to change work into play, conviction into opinion, and philosophy into philodoxy.

With regard to this second edition, I have tried, as was but fair, to do all I could in order to remove, as far as possible, the difficulties and obscurities which, not perhaps without my fault, have misled even acute thinkers in judging of my book. In the propositions themselves, and their proofs, likewise in the form and completeness of the whole plan, I have found nothing to alter, which is due partly to the long-continued examination to which I had subjected them, before submitting them to the public, and partly to the nature of the subject itself. For pure speculative reason is so constituted that it forms a true organism, in which everything is organic, the whole being there for the [p. xxxviii] sake of every part, and every part for the sake of the whole, so that the smallest imperfection, whether a fault or a deficiency, must inevitably betray itself in use. I venture to hope that this system will maintain itself unchanged for the future also. It is not self-conceit which justifies me in this confidence, but the experimental evidence produced by the identity of the result, whether we proceed progressively from the smallest elements to the whole of pure reason, or retrogressively from the whole (for this also is given by the practical objects of reason) to every single part; the fact being, that an attempt at altering even the smallest item produces at once contradictions, not only in the system, but in human reason in general. With regard to the style, however, much remains to be done; and for that purpose, I have endeavoured to introduce several improvements into this second edition, which are intended to remove, first, misapprehensions in the Æsthetic, especially with regard to the concept of time: secondly, obscurities in the deduction of the concepts of the understanding: thirdly, a supposed want of sufficient evidence, in proving the propositions of the pure understanding: fourthly, the false interpretation put on the paralogisms with which we charged rational psychology. To this point (only to the end of the first chapter of transcendental Dialectic) do the changes [p. xxxix] of style and representation1 extend, and no further. Time was too short for doing more, nor did I, with regard to the [p. xl] rest, meet with any misapprehensions on the part of [p. xli] competent and impartial judges. These, even though I must not name them with that praise which is due to them, will easily perceive in the proper place, that I have paid careful attention to their remarks. [p. xlii]

These improvements, however, entail a small loss to the reader. It was inevitable, without making the book too voluminous, to leave out or abridge several passages which, though not essential to the completeness of the whole, may yet, as useful for other purposes, be missed by some readers. Thus only could I gain room for my new and more intelligible representation of the subject which, though it changes absolutely nothing with regard to propositions, and even to proofs, yet deviates so considerably from the former, in the method of the treatment here and there, that mere additions and interpolations would not have been sufficient. This small loss, which every reader may easily supply by reference to the first edition, will I hope be more than compensated for by the greater clearness of the present.

I have observed with pleasure and thankfulness in various publications (containing either reviews or separate essays) that the spirit of thoroughness is not yet dead in Germany, but has only been silenced for a short time by the clamour of a fashionable and pretentious licence of thought, and that the difficulties [p. xliii] which beset the thorny path of my critique, which is to lead to a truly scientific and, as such, permanent, and therefore most necessary, science of pure reason, have not discouraged bold and clear heads from mastering my book. To these excellent men, who so happily blend thorough knowledge with a talent for lucid exposition (to which I can lay no claim), I leave the task of bringing my, in that respect far from perfect, work to greater perfection. There is no danger of its being refuted, though there is of its being misunderstood. For my own part, I cannot henceforth enter on controversies, though I shall carefully attend to all hints, whether from friends or opponents, in order to utilise them in a future elaboration of the whole system, according to the plan traced out in this propaedeutic. As during these labours I have advanced pretty far in years (this very month, into my sixty-fourth year), I must be careful in spending my time, if I am to carry out my plan, of furnishing a metaphysic of nature, and a metaphysic of morals, in confirmation of the truth of my critique both of speculative and of practical reason, and must leave the elucidation of such obscurities as could at first be hardly avoided [p. xliv] in such a work, and likewise the defence of the whole, to those excellent men who have made it their own. At single points every philosophical treatise may be pricked (for it cannot be armed at all points, like a mathematical one), while yet the organic structure of the system, considered as a whole, has not therefore to apprehend the slightest danger. Few only have that pliability of intellect to take in the whole of a system, if it is new; still fewer have an inclination for it, because they dislike every innovation. If we take single passages out of their connection, and contrast them with each other, it is easy to pick out apparent contradictions, particularly in a work written with all the freedom of a running speech. In the eyes of those who rely on the judgment of others, such contradictions may throw an unfavourable light on any work; but they are easily removed, if we ourselves have once grasped the idea of the whole. And, if a theory possesses stability in itself, then this action and reaction of praise and blame, which at first seemed so dangerous, serve only in time to rub off its superficial inequalities: nay, secure to it, in a short time, the requisite elegance also, if only men of insight, impartiality, and true popularity will devote themselves to its study.

Königsberg, April, 1787.

SUPPLEMENT III

SUPPLEMENT IV

[See page 1]

INTRODUCTION

I

Of the Difference between Pure and Empirical Knowledge

That all our knowledge begins with experience there can be no doubt. For how should the faculty of knowledge be called into activity, if not by objects which affect our senses, and which either produce representations by themselves, or rouse the activity of our understanding to compare, to connect, or to separate them; and thus to convert the raw material of our sensuous impressions into a knowledge of objects, which we call experience? In respect of time, therefore, no knowledge within us is antecedent to experience, but all knowledge begins with it.

But although all our knowledge begins with experience, it does not follow that it arises from experience. For it is quite possible that even our empirical experience is a compound of that which we receive through impressions, and of that which our own faculty of knowledge (incited only by sensuous impressions), supplies from itself, a supplement which we do not distinguish from that raw material, until long practice has roused our attention and rendered us capable of separating one from the other.

It is therefore a question which deserves at least closer investigation, and cannot be disposed of at first sight, whether there exists a knowledge independent of experience, and even of all impressions of the senses? Such knowledge is called a priori, and distinguished from empirical knowledge, which has its sources a posteriori, that is, in experience.

This term a priori, however, is not yet definite enough to indicate the full meaning of our question. For people are wont to say, even with regard to knowledge derived from experience, that we have it, or might have it, a priori, because we derive it from experience, not immediately, but from a general rule, which, however, has itself been derived from experience. Thus one would say of a person who undermines the foundations of his house, that he might have known a priori that it would tumble down, that is, that he need not wait for the experience of its really tumbling down. But still he could not know this entirely a priori, because he had first to learn from experience that bodies are heavy, and will fall when their supports are taken away.

We shall therefore, in what follows, understand by knowledge a priori knowledge which is absolutely independent of all experience, and not of this or that experience only. Opposed to this is empirical knowledge, or such as is possible a posteriori only, that is, by experience. Knowledge a priori, if mixed up with nothing empirical, is called pure. Thus the proposition, for example, that every change has its cause, is a proposition a priori, but not pure: because change is a concept which can only be derived from experience.

II

We are in Possession of Certain Cognitions a priori, and even the Ordinary Understanding is never without them

All depends here on a criterion, by which we may safely distinguish between pure and empirical knowledge. Now experience teaches us, no doubt, that something is so or so, but not that it cannot be different. First, then, if we have a proposition, which is thought, together with its necessity, we have a judgment a priori; and if, besides, it is not derived from any proposition, except such as is itself again considered as necessary, we have an absolutely a priori judgment. Secondly, experience never imparts to its judgments true or strict, but only assumed or relative universality (by means of induction), so that we ought always to say, so far as we have observed hitherto, there is no exception to this or that rule. If, therefore, a judgment is thought with strict universality, so that no exception is admitted as possible, it is not derived from experience, but valid absolutely a priori. Empirical universality, therefore, is only an arbitrary extension of a validity which applies to most cases, to one that applies to all: as, for instance, in the proposition, all bodies are heavy. If, on the contrary, strict universality is essential to a judgment, this always points to a special source of knowledge, namely, a faculty of knowledge a priori. Necessity, therefore, and strict universality are safe criteria of knowledge a priori, and are inseparable one from the other. As, however, in the use of these criteria, it is sometimes easier to show the contingency than the empirical limitation1 of judgments, and as it is sometimes more convincing to prove the unlimited universality which we attribute to a judgment than its necessity, it is advisable to use both criteria separately, each being by itself infallible.

That there really exist in our knowledge such necessary, and in the strictest sense universal, and therefore pure judgments a priori, is easy to show. If we want a scientific example, we have only to look to any of the propositions of mathematics; if we want one from the sphere of the ordinary understanding, such a proposition as that each change must have a cause, will answer the purpose; nay, in the latter case, even the concept of cause contains so clearly the concept of the necessity of its connection with an effect, and of the strict universality of the rule, that it would be destroyed altogether if we attempted to derive it, as Hume does, from the frequent concomitancy of that which happens with that which precedes, and from a habit arising thence (therefore from a purely subjective necessity), of connecting representations. It is possible even, without having recourse to such examples in proof of the reality of pure propositions a priori within our knowledge, to prove their indispensability for the possibility of experience itself, thus proving it a priori. For whence should experience take its certainty, if all the rules which it follows were always again and again empirical, and therefore contingent and hardly fit to serve as first principles? For the present, however, we may be satisfied for having shown the pure employment of the faculty of our knowledge as a matter of fact, with the criteria of it.

Not only in judgments, however, but even in certain concepts, can we show their origin a priori. Take away, for example, from the concept of a body, as supplied by experience, everything that is empirical, one by one; such as colour, hardness or softness, weight, and even impenetrability, and there still remains the space which the body (now entirely vanished) occupied: that you cannot take away. And in the same manner, if you remove from your empirical concept of any object, corporeal or incorporeal, all properties which experience has taught you, you cannot take away from it that property by which you conceive it as a substance, or inherent in a substance (although such a concept contains more determinations than that of an object in general). Convinced, therefore, by the necessity with which that concept forces itself upon you, you will have to admit that it has its seat in your faculty of knowledge a priori.

SUPPLEMENT V

[See page 6]

Empirical judgments, as such, are all synthetical; for it would be absurd to found an analytical judgment on experience, because, in order to form such a judgment, I need not at all step out of my concept, or appeal to the testimony of experience. That a body is extended, is a proposition perfectly certain a priori, and not an empirical judgment. For, before I call in experience, I am already in possession of all the conditions of my judgment in the concept of body itself. I have only to draw out from it, according to the principle of contradiction, the required predicate, and I thus become conscious, at the same time, of the necessity of the judgment, which experience could never teach me. But, though I do not include the predicate of gravity in the general concept of body, that concept, nevertheless, indicates an object of experience through one of its parts: so that I may add other parts also of the same experience, besides those which belonged to the former concept. I may, first, by an analytical process, realise the concept of body, through the predicates of extension, impermeability, form, etc., all of which are contained in it. Afterwards I expand my knowledge, and looking back to the experience from which my concept of body was abstracted, I find gravity always connected with the before-mentioned predicates, and therefore I add it synthetically to that concept as a predicate. It is, therefore, experience on which the possibility of the synthesis of the predicate of gravity with the concept of body is founded: because both concepts, though neither of them is contained in the other, belong to each other, though accidentally only, as parts of a whole, namely, of experience, which is itself a synthetical connection of intuitions.

SUPPLEMENT VI

[See page 8]

V

In all Theoretical Sciences of Reason Synthetical Judgments a priori are contained as Principles

1. All mathematical judgments are synthetical. This proposition, though incontestably certain, and very important to us for the future, seems to have hitherto escaped the observation of those who are engaged in the anatomy of human reason: nay, to be directly opposed to all their conjectures. For as it was found that all mathematical conclusions proceed according to the principle of contradiction (which is required by the nature of all apodictic certainty), it was supposed that the fundamental principles of mathematics also rested on the authority of the same principle of contradiction. This, however, was a mistake: for though a synthetical proposition may be understood according to the principle of contradiction, this can only be if another synthetical proposition is presupposed, from which the latter is deduced, but never by itself. First of all, we ought to observe, that mathematical propositions, properly so called, are always judgments a priori, and not empirical, because they carry along with them necessity, which can never be deduced from experience. If people should object to this, I am quite willing to confine my statement to pure mathematics, the very concept of which implies that it does not contain empirical, but only pure knowledge a priori.

At first sight one might suppose indeed that the proposition 7 + 5 = 12 is merely analytical, following, according to the principle of contradiction, from the concept of a sum of 7 and 5. But, if we look more closely, we shall find that the concept of the sum of 7 and 5 contains nothing beyond the union of both sums into one, whereby nothing is told us as to what this single number may be which combines both. We by no means arrive at a concept of Twelve, by thinking that union of Seven and Five; and we may analyse our concept of such a possible sum as long as we will, still we shall never discover in it the concept of Twelve. We must go beyond these concepts, and call in the assistance of the intuition corresponding to one of the two, for instance, our five fingers, or, as Segner does in his arithmetic, five points, and so by degrees add the units of the Five, given in intuition, to the concept of the Seven. For I first take the number 7, and taking the intuition of the fingers of my hand, in order to form with it the concept of the 5, I gradually add the units, which I before took together, to make up the number 5, by means of the image of my hand, to the number 7, and I thus see the number 12 arising before me. That 5 should be added to 7 was no doubt implied in my concept of a sum 7 + 5, but not that that sum should be equal to 12. An arithmetical proposition is, therefore, always synthetical, which is seen more easily still by taking larger numbers, where we clearly perceive that, turn and twist our conceptions as we may, we could never, by means of the mere analysis of our concepts and without the help of intuition, arrive at the sum that is wanted.

Nor is any proposition of pure geometry analytical. That the straight line between two points is the shortest, is a synthetical proposition. For my concept of straight contains nothing of magnitude (quantity), but a quality only. The concept of the shortest is, therefore, purely adventitious, and cannot be deduced from the concept of the straight line by any analysis whatsoever. The aid of intuition, therefore, must be called in, by which alone the synthesis is possible.

[It is true that some few propositions, presupposed by the geometrician, are really analytical, and depend on the principle of contradiction: but then they serve only, like identical propositions, to form the chain of the method, and not as principles. Such are the propositions, a = a, the whole is equal to itself, or (a + b) > a, that the whole is greater than its part. And even these, though they are valid according to mere concepts, are only admitted in mathematics, because they can be represented in intuition.1 ] What often makes us believe that the predicate of such apodictic judgments is contained in our concept, and the judgment therefore analytical, is merely the ambiguous character of the expression. We are told that we ought to join in thought a certain predicate to a given concept, and this necessity is inherent in the concepts themselves. But the question is not what we ought to join to the given concept, but what we really think in it, though confusedly only, and then it becomes clear that the predicate is no doubt inherent in those concepts by necessity, not, however, as thought in the concept itself, but by means of an intuition, which must be added to the concept.

2. Natural science (physica) contains synthetical judgments a priori as principles. I shall adduce, as examples, a few propositions only, such as, that in all changes of the material world the quantity of matter always remains unchanged: or that in all communication of motion, action and reaction must always equal each other. It is clear not only that both convey necessity, and that, therefore, their origin is a priori, but also that they are synthetical propositions. For in the concept of matter I do not conceive its permanency, but only its presence in the space which it fills. I therefore go beyond the concept of matter in order to join something to it a priori, which I did not before conceive in it. The proposition is, therefore, not analytical, but synthetical, and yet a priori, and the same applies to the other propositions of the pure part of natural science.

3. Metaphysic, even if we look upon it as hitherto a tentative science only, which, however, is indispensable to us, owing to the very nature of human reason, is meant to contain synthetical knowledge a priori. Its object is not at all merely to analyse such concepts as we make to ourselves of things a priori, and thus to explain them analytically, but to expand our knowledge a priori. This we can only do by means of concepts which add something to a given concept that was not contained in it; nay, we even attempt, by means of synthetical judgments a priori, to go so far beyond a given concept that experience itself cannot follow us: as, for instance, in the proposition that the world must have a first beginning. Thus, according at least to its intentions, metaphysic consists merely of synthetical propositions a priori.

VI

The General Problem of Pure Reason

Much is gained if we are able to bring a number of investigations under the formula of one single problem. For we thus not only facilitate our own work by defining it accurately, but enable also everybody else who likes to examine it to form a judgment, whether we have really done justice to our purpose or not. Now the real problem of pure reason is contained in the question, How are synthetical judgments a priori possible?

That metaphysic has hitherto remained in so vacillating a state of ignorance and contradiction is entirely due to people not having thought sooner of this problem, or perhaps even of a distinction between analytical and synthetical judgments. The solution of this problem, or a sufficient proof that a possibility which is to be explained does in reality not exist at all, is the question of life or death to metaphysic. David Hume, who among all philosophers approached nearest to that problem, though he was far from conceiving it with sufficient definiteness and universality, confining his attention only to the synthetical proposition of the connection of an effect with its causes (principium causalitatis), arrived at the conclusion that such a proposition a priori is entirely impossible. According to his conclusions, everything which we call metaphysic would turn out to be a mere delusion of reason, fancying that it knows by itself what in reality is only borrowed from experience, and has assumed by mere habit the appearance of necessity. If he had grasped our problem in all its universality, he would never have thought of an assertion which destroys all pure philosophy, because he would have perceived that, according to his argument, no pure mathematical science was possible either, on account of its certainly containing synthetical propositions a priori; and from such an assertion his good sense would probably have saved him.

On the solution of our problem depends, at the same time, the possibility of the pure employment of reason, in establishing and carrying out all sciences which contain a theoretical knowledge a priori of objects, i.e. the answer to the questions

How is pure mathematical science possible?

How is pure natural science possible?

As these sciences really exist, it is quite proper to ask, How they are possible? for that they must be possible, is proved by their reality.1

But as to metaphysic, the bad progress which it has hitherto made, and the impossibility of asserting of any of the metaphysical systems yet brought forward that it really exists, so far as its essential aim is concerned, must fill every one with doubts as to its possibility.

Yet, in a certain sense, this kind of knowledge also must be looked upon as given, and though not as a science, yet as a natural disposition (metaphysica naturalis) metaphysic is real. For human reason, without being moved merely by the conceit of omniscience, advances irresistibly, and urged on by its own need, to questions such as cannot be answered by any empirical employment of reason, or by principles thence derived, so that we may really say, that all men, as soon as their reason became ripe for speculation, have at all times possessed some kind of metaphysic, and will always continue to possess it. And now it will also have to answer the question

How is metaphysic possible, as a natural disposition? that is how does the nature of universal human reason give rise to questions which pure reason proposes to itself, and which it is urged on by its own need to answer as well as it can?

As, however, all attempts which have hitherto been made at answering these natural questions (for instance, whether the world has a beginning, or exists from all eternity) have always led to inevitable contradictions, we cannot rest satisfied with the mere natural disposition to metaphysic, that is, with the pure faculty of reason itself, from which some kind of metaphysic (whatever it may be) always arises; but it must be possible to arrive with it at some certainty as to our either knowing or not knowing its objects; that is, we must either decide that we can judge of the objects of these questions, or of the power or want of power of reason, in deciding anything upon them, — therefore that we can either enlarge our pure reason with certainty, or that we have to impose on it fixed and firm limits. This last question, which arises out of the former more general problem, would properly assume this form,

How is metaphysic possible, as a science?

The critique of reason leads, therefore, necessarily, to true science, while its dogmatical use, without criticism, lands us in groundless assertions, to which others, equally specious, can always be opposed, that is, in scepticism.

Nor need this science be very formidable by its great prolixity, for it has not to deal with the objects of reason, the variety of which is infinite, but with reason only, and with problems, suggested by reason and placed before it, not by the nature of things, which are different from it, but by its own nature; so that, if reason has only first completely understood its own power, with reference to objects given to it in experience, it will have no difficulty in determining completely and safely the extent and limits of its attempted application beyond the limits of all experience.

We may and must therefore regard all attempts which have hitherto been made at building up a metaphysic dogmatically, as non-avenu. For the mere analysis of the concepts that dwell in our reason a priori, which has been attempted in one or other of those metaphysical systems, is by no means the aim, but only a preparation for true metaphysic, namely, the answer to the question, how we can enlarge our knowledge a priori synthetically; nay, it is utterly useless for that purpose, because it only shows what is contained in those concepts, but not by what process a priori we arrive at them, in order thus to determine the validity of their employment with reference to all objects of knowledge in general. Nor does it require much self-denial to give up these pretensions, considering that the undeniable and, in the dogmatic procedure, inevitable contradictions of reason with itself, have long deprived every system of metaphysic of all authority. More firmness will be required in order not to be deterred by difficulties from within and resistance from without, from trying to advance a science, indispensable to human reason (a science of which we may lop off every branch, but will never be able to destroy the root), by a treatment entirely opposed to all former treatments, which promises, at last, to ensure the successful and fruitful growth of metaphysical science.

SUPPLEMENT VII

[See page 10]

Still less ought we to except here a criticism on the books and systems treating of pure reason, but only on the faculty of pure reason itself. It is only if we are in possession of this, that we possess a safe criterion for estimating the philosophical value of old and new works on this subject. Otherwise, an unqualified historian and judge does nothing but criticise the groundless assertions of others by means of his own, which are equally groundless.

SUPPLEMENT VIII

[See page 20]

4. Space is represented as an infinite given quantity. Now it is quite true that every concept is to be thought as a representation, which is contained in an infinite number of different possible representations (as their common characteristic), and therefore comprehends them: but no concept, as such, can be thought as if it contained in itself an infinite number of representations. Nevertheless, space is so thought (for all parts of infinite space exist simultaneously). Consequently, the original representation of space is an intuition a priori, and not a concept.

§ 3

Transcendental Exposition of the Concept of Space

I understand by transcendental exposition (Erörterung), the explanation of a concept, as of a principle by which the possibility of other synthetical cognitions a priori can be understood. For this purpose it is necessary, 1. That such cognitions really do flow from the given concept. 2. That they are possible only under the presupposition of a given mode of explanation of such concept.

Geometry is a science which determines the properties of space synthetically, and yet a priori. What then must be the representation of space, to render such a knowledge of it possible? It must be originally intuitive; for it is impossible from a mere concept to deduce propositions which go beyond that concept, as we do in geometry (Introduction V. See Suppl. VI). That intuition, however, must be a priori, that is, it must exist within us before any perception of the object, and must therefore be pure, not empirical intuition. For all geometrical propositions are apodictic, that is, connected with the consciousness of their necessity, as for instance the proposition, that space has only three dimensions; and such propositions cannot be empirical judgments, nor conclusions from them (Introduction II. See Suppl. IV. ii).

How then can an external intuition dwell in the mind anterior to the objects themselves, and in which the concept of objects can be determined a priori? Evidently not otherwise than so far as it has its seat in the subject only, as the formal condition under which the subject is affected by the objects and thereby is receiving an immediate representation, that is, intuition of them; therefore as a form of the external sense in general.

It is therefore by our explanation only that the possibility of geometry as a synthetical science a priori becomes intelligible. Every other explanation, which fails to account for this possibility, can best be distinguished from our own by that criterion, although it may seem to have some similarity with it.

SUPPLEMENT IX

[See page 22]

With the exception of space there is no other subjective representation, referring to something external, that could be called a priori objective. For from none of them can we derive synthetical propositions a priori, as we can from the intuition in space § 3. (See Suppl. VIII.) Strictly speaking, therefore, they can claim no ideality at all, though they agree with the representation of space in this, that they belong only to the subjective nature of sensibility, for instance, of sight, of hearing, and feeling, through the sensations of colours, sounds, and heat. All these, however, being sensations only, and not intuitions, do not help us by themselves to know any object, least of all a priori.

SUPPLEMENT X

[See page 26]

§ 5

Transcendental Exposition of the Concept of Time

I can here refer to No. iii. p. 27, where, for the sake of brevity, I have placed what is properly transcendental under the head of metaphysical exposition. Here I only add that the concept of change, and with it the concept of motion (as change of place), is possible only through and in the representation of time; and that, if this representation were not intuitive (internal) a priori, no concept, whatever it be, could make us understand the possibility of a change, that is, of a connection of contradictorily opposed predicates (for instance, the being and not-being of one and the same thing in one and the same place) in one and the same object. It is only in time that both contradictorily opposed determinations can be met with in the same object, that is, one after the other. Our concept of time, therefore, exhibits the possibility of as many synthetical cognitions a priori as are found in the general doctrine of motion, which is very rich in them.

SUPPLEMENT XI

[See page 39]

II. As a confirmation of this theory of the ideality both of the external and of the internal sense, and therefore of all objects of the senses as mere phenomena, we may particularly remark, that everything in our knowledge which belongs to intuition (excluding therefore the feelings of pain and pleasure, and the will, which are no knowledge at all) contains nothing but mere relations, namely, of the places in an intuition (extension), change of places (motion), and laws, according to which that change is determined (moving forces). Nothing is told us thereby as to what is present in the place, or what, besides the change of place, is active in the things. A thing by itself, however, cannot be known by mere relations, and we may, therefore, fairly conclude that, as the external sense gives us nothing but representations of relations, that sense can contain in its representation only the relation of an object to the subject, and not what is inside the object by itself. The same applies to internal intuition. Not only do the representations of the external senses constitute its proper material with which we fill our mind, but time, in which these representations are placed, and which precedes even our consciousness of them in experience, nay, forms the formal condition of the manner in which we place them in the mind, contains itself relations of succession, coexistence, and that which must be coexistent with succession, namely, the permanent. Now that which, as a representation, can precede every act of thinking something, is the intuition: and, if it contains nothing but relations, then the form of intuition. As this represents nothing except what is being placed in the mind, it can itself be the manner only in which the mind, through its own activity, that is, by this placing of its representation, is affected by itself, in other words, an internal sense with respect to its form. Whatever is represented by a sense is so far always phenomenal, and we should therefore have either to admit no internal sense at all, or the subject, which is its object, could be represented by it as phenomenal only, and not, as it might judge of itself, if its intuition were spontaneous only, that is, if it were intellectual. The difficulty here lies wholly in this, how a subject can have an internal intuition of itself: but this difficulty is common to every theory. The consciousness of self (apperception) is the simple representation of the ego, and if by it alone all the manifold (representations) in the subject were given spontaneously, the inner intuition would be intellectual. In man this consciousness requires internal perception of the manifold, which is previously given in the subject, and the manner in which this is given in the mind without spontaneity, must, on account of this difference, be called sensibility. If the faculty of self-consciousness is to seek for, that is, to apprehend, what lies in the mind, it must affect the mind, and can thus only produce an intuition of itself. The form of this, which lay antecedently in the mind, determines the manner in which the manifold exists together in the mind, namely, in the representation of time. The intuition of self, therefore, is not, as if it could represent itself immediately and as spontaneously and independently active, but according to the manner in which it is internally affected, consequently as it appears to itself, not as it is.

III. If I say that the intuition of external objects and the self-intuition of the mind, represent both (viz. the objects and the mind) in space and time, as they affect our senses, that is, as they appear, I do not mean, that these objects are mere illusion. For the objects, as phenomena, nay, even the properties which we ascribe to them, are always looked upon as something really given: and all we do is, that, as their quality depends only on the manner of intuition on the part of the subject in relation to a given object, we distinguish the object, as phenomenon, from itself, as an object by itself. Thus, if I assert that the quality of space and time, according to which, as a condition of their existence, I accept both external objects and my own soul, lies in my manner of intuition and not in these objects by themselves, I do not mean to say that bodies seem only to exist outside me, or that my soul seems only to be given in my self-consciousness. It would be my own fault, if I changed that, which I ought to count as phenomenal, into mere illusion.1

This cannot happen, however, according to our principle of the ideality of all sensuous intuitions; on the contrary, it is only when we attribute objective reality to those forms of intuition that everything is changed inevitably into mere illusion. For if we take space and time as properties that ought to exist as possible in things by themselves, and then survey the absurdities in which we should be involved in having to admit that two infinite things, which are not substances, nor something inherent in substances, but nevertheless must be something existing, nay, the necessary condition of the existence of all things, would remain, even if all existing things were removed, we really cannot blame the good Bishop Berkeley for degrading bodies to mere illusion. Nay, it would follow that even our own existence, which would thus be made dependent on the independent reality of such a non-entity as time, must become a mere illusion, an absurdity which hitherto no one has been guilty of.

IV. In natural theology, where we think of an object which not only can never be an object of intuition to us, but which even to itself can never be an object of sensuous intuition, great care is taken to remove all conditions of space and time from its intuition (for all its knowledge must be intuitive, and not thought, which always involves limitation). But how are we justified in doing this, when we have first made space and time forms of things by themselves, such as would remain as conditions of the existence of things a priori, even if the things themselves had been removed? If conditions of all existence, they would also be conditions of the existence of God. If we do not wish to change space and time into objective forms of all things, nothing remains but to accept them as subjective forms of our external as well as internal intuition, which is called sensuous, for the very reason that it is not originally spontaneous, that is such, that it could itself give us the existence of the objects of intuition (such an intuition, so far as we can understand, can belong to the First Being only), but dependent on the existence of objects, and therefore possible only, if the faculty of representation in the subject is affected by them.

It is not necessary, moreover, that we should limit this intuition in space and time to the sensibility of man; it is quite possible that all finite thinking beings must necessarily agree with us on this point (though we cannot decide this). On account of this universal character, however, it does not cease to be sensibility, for it always is, and remains derivative (intuitus derivativus), not original (intuitus originarius), and therefore not intellectual intuition. For the reason mentioned before, the latter intuition seems only to belong to the First Being, and never to one which is dependent, both in its existence and its intuition (which intuition determines its existence with reference to given objects). This latter remark, however, must only be taken as an illustration of our æsthetic theory, and not as a proof.

Conclusion of the Transcendental Æsthetic

Here, then, we have one of the requisites for the solution of the general problem of transcendental philosophy, How are synthetical propositions a priori possible? namely, pure intuitions a priori, space and time. In them we find, if in a judgment a priori we want to go beyond a given concept, that which can be discovered a priori, not in the concept, but in the intuition corresponding to it, and can be connected with it synthetically. For this very reason, however, such judgments can never go beyond the objects of the senses, but are valid only for objects of possible experience.

SUPPLEMENT XII

[See page 69]

§ 11

This table of categories suggests some interesting considerations, which possibly may have important consequences with regard to the scientific form of all knowledge of reason. For it is clear that such a table will be extremely useful, nay, indispensable, in the theoretical part of philosophy, in order to trace the complete plan of a whole science, so far as it rests on concepts a priori, and to divide it systematically according to fixed principles, because that table contains all elementary concepts of the understanding in their completeness, nay, even the form of a system of them in the human understanding, and indicates therefore all the momenta of a projected speculative science, nay, even their order. Of this I have given an example elsewhere.1 Here follow some of the considerations.

The first is, that this table, which contains four classes of the concepts of the understanding, may, in the first instance, be divided into two sections, the former of which refers to objects of intuition (pure, as well as empirical), the latter to the existence of those objects (either in their relation to each other, or to the understanding).

The first section I shall call that of the mathematical, the second, that of the dynamical categories. The first section has no correlates, which are met with in the second section only. Must not this difference have some ground in the nature of the understanding?

Our second remark is, that in every class there is the same number of categories, namely three, which again makes us ponder, because generally all division a priori by means of concepts must be dichotomy. It should be remarked also, that the third category always arises from the combination of the second with the first. Thus totality is nothing but plurality considered as unity; limitation nothing but reality connected with negation; community is the casuality of a substance as determining another reciprocally; lastly, necessity, the existence which is given by possibility itself. It must not be supposed, however, that therefore the third category is only a derivative, and not a primary concept of the pure understanding. For the joining of the first and second concepts, in order to produce the third, requires an independent act of the understanding, which is not identical with the act that produces the first and second concepts. Thus the concept of a number (which belongs to the category of totality) is not always possible when we have the concepts of plurality and unity (for instance, in the concept of the infinite); nor can we understand by simply combining the concept of a cause and that of a substance, the influence, that is, how a substance can become the cause of something in another substance. This shows that a separate act of the understanding is here required, and the same applies to all the rest.

Third observation. With regard to one category, namely, that of community, which is found in the third class, its accordance with the form of a disjunctive judgment, which corresponds to it in the table of logical functions, is not so evident as elsewhere.

In order to become quite certain of that accordance, we must remark that in all disjunctive judgments their sphere (that is, all that is contained in them) is represented as a whole, divided into parts (the subordinate concepts), and that, as one of them cannot be contained under the other, they are conceived as co-ordinate, not as subordinate, determining each other, not in one direction only, as in a series, but reciprocally, as in an aggregate (if one member of the division is given, all the rest are excluded, and vice versa).

A similar connection is conceived in a whole of things, in which one, as effect, is not subordinated to another as the cause of its existence, but is co-ordinated with it, simultaneously and reciprocally, as cause of the determination of the other (as, for instance, in a body of which the parts reciprocally attract and repel each other). This is a kind of connection totally different from that which exists in a mere relation of cause to effect (of ground to consequence), for here the consequence does not reciprocally determine the ground again, nor (as in the case of the Creator and the creation) constitute with it a whole. The process of the understanding, in representing to itself the sphere of a divided concept, is the same as that by which it thinks a thing as divisible: and in the same manner in which, in the former, the members of a division exclude each other, and are yet connected in one sphere, the understanding represents to itself the parts of the latter as existing (as substances), each independent of the rest, and yet united in a whole.

§ 12

In the transcendental philosophy of the ancients there is another chapter containing concepts of the understanding which, though they are not counted among the categories, are yet considered by them as concepts a priori of objects. If so, they would increase the number of the categories, which cannot be. They are set forth in the famous proposition of the Schoolmen, ‘quodlibet ens est unum, verum, bonum.’ Now, although the inferences to be drawn from this principle (yielding nothing but tautological propositions) were very meagre, so that modern metaphysicians mention it almost by courtesy only, a thought which has maintained itself so long, however empty it may seem, deserves an investigation with regard to its origin, nay, leads us to suspect that it may have its foundation in some rule of the understanding which, as often happens, has only been wrongly interpreted. What are supposed to be transcendental predicates of things are nothing but logical requirements and criteria of all knowledge of things in general, whereby that knowledge is founded on the categories of quantity, namely, unity, plurality, and totality. Only, instead of taking them as materially belonging to the possibility of things by themselves, they (the predicates, or rather those who employed them) used them, in fact, in their formal meaning only, as forming a logical requisite for every kind of knowledge, and yet incautiously made these criteria of thought to be properties of the things by themselves. In every cognition of an object there is unity of concept, which may be called qualitative unity, so far as we think by it only the unity in the comprehension of the manifold material of our knowledge: as, for instance, the unity of the subject in a play, or a speech, or a fable. Secondly, there is truth, in respect to the deductions from it. The more true deductions can be made from a given concept, the more criteria are there of its objective reality. This might be called the qualitative plurality of criteria, which belong to a concept as their common ground (but are not conceived in it, as quantity). Thirdly, there is completeness, which consists in this, that the plurality together leads back to the unity of the concept, according completely with this and with no other concept, which may be called the qualitative completeness (totality). This shows that these logical criteria of the possibility of knowledge in general do nothing but change the three categories of quantity, in which the unity in the production of the quantum must throughout be taken as homogeneous, for the purpose of connecting heterogeneous elements of knowledge also in one consciousness, by means of the quality of the cognition as the principle of the connection. Thus the criterion of the possibility of a concept (but not of its object) is the definition of it, in which the unity of the concept, the truth of all that may be immediately deduced from it, and lastly, the completeness of what has been deduced from it, supply all that is necessary for the constitution of the whole concept. In the same manner the criterion of an hypothesis consists, first, in the intelligibility of the ground which has been admitted for the sake of explanation, or of its unity (without any auxiliary hypothesis); secondly, in the truth of the consequences to be deduced from it (their accordance with themselves and with experience); and lastly, in the completeness of the ground admitted for the explanation of these consequences, which point back to neither more nor less than what was admitted in the hypothesis, and agree in giving us again, analytically a posteriori, what had been thought synthetically a priori. The concepts of unity, truth, and perfection, therefore, do not supplement the transcendental table of the categories, as if it were imperfect, but they serve only, after the relation of these concepts to objects has been entirely set aside, to bring their employment under general logical rules, for the agreement of knowledge with itself.

SUPPLEMENT XIII

[See page 79]

Locke, for want of this reflection, and because he met with pure concepts of the understanding in experience, derived them also from experience, and yet acted so inconsistently that he attempted to use them for knowledge which far exceeds all limits of experience. David Hume saw that, in order to be able to do this, these concepts ought to have their origin a priori; but as he could not explain how it was possible that the understanding should be constrained to think concepts, which by themselves are not united in the understanding, as necessarily united in the object, and never thought that possibly the understanding might itself, through these concepts, be the author of that experience in which its objects are found, he was driven by necessity to derive them from experience (namely, from a subjective necessity, produced by frequent association in experience, which at last is wrongly supposed to be objective, that is, from habit). He acted, however, very consistently, by declaring it to be impossible to go with these concepts, and with the principles arising from them, beyond the limits of experience. This empirical deduction, which was adopted by both philosophers, cannot be reconciled with the reality of our scientific knowledge a priori, namely, pure mathematics and general natural science, and is therefore refuted by facts. The former of these two celebrated men opened a wide door to fantastic extravagance, because reason, if it has once established such pretensions, can no longer be checked by vague praises of moderation; the other, thinking that he had once discovered so general an illusion of our faculty of knowledge, which had formerly been accepted as reason, gave himself over entirely to scepticism. We now intend to make the experiment whether it is not possible to conduct reason safely between these two rocks, to assign to her definite limits, and yet to keep open for her the proper field for all her activities?

I shall merely premise an explanation of what I mean by the categories. They are concepts of an object in general by which its intuition is regarded as determined with reference to one of the logical functions in judgments. Thus the function of the categorical judgment was that of the relation of the subject to the predicate; for instance, all bodies are divisible. Here, however, with reference to the pure logical employment of the understanding, it remained undetermined to which of the two concepts the function of the subject, or the predicate, was to be assigned. For we could also say, some divisible is body. But by bringing the concept of body under the category of substance, it is determined that its empirical intuition in experience must always be considered as subject and never as predicate only. The same applies to all other categories.

SUPPLEMENT XIV

[See page 79]

OF THE DEDUCTION OF THE PURE CONCEPTS OF THE UNDERSTANDING

Second Section

Transcendental Deduction of the Pure Concepts of the Understanding

§ 15

Of the Possibility of Connecting (conjunctio) in General

The manifold of representations may be given in an intuition which is purely sensuous, that is, nothing but receptivity, and the form of that intuition may lie a priori in our faculty of representation, without being anything but the manner in which a subject is affected. But the connection (conjunctio) of anything manifold can never enter into us through the senses, and cannot be contained, therefore, already in the pure form of sensuous intuition, for it is a spontaneous act of the power of representation; and as, in order to distinguish this from sensibility, we must call it understanding, we see that all connecting, whether we are conscious of it or not, and whether we connect the manifold of intuition or several concepts together, and again, whether that intuition be sensuous or not sensuous, is an act of the understanding. This act we shall call by the general name of synthesis, in order to show that we cannot represent to ourselves anything as connected in the object, without having previously connected it ourselves, and that of all representations connection is the only one which cannot be given through the objects, but must be carried out by the subject itself, because it is an act of its spontaneity. It can be easily perceived that this act must be originally one and the same for every kind of connection, and that its dissolution, that is, the analysis, which seems to be its opposite, does always presuppose it. For where the understanding has not previously connected, there is nothing for it to disconnect, because, as connected, it could only be given by the understanding to the faculty of representation.

But the concept of connection includes, besides the concept of the manifold and the synthesis of it, the concept of the unity of the manifold also. Connection is representation of the synthetical unity of the manifold.1

The representation of that unity cannot therefore be the result of the connection; on the contrary, the concept of the connection becomes first possible by the representation of unity being added to the representation of the manifold. And this unity, which precedes a priori all concepts of connection, must not be mistaken for that category of unity of which we spoke on p. 68; for all categories depend on logical functions in judgments, and in these we have already connection, and therefore unity of given concepts. The category, therefore, presupposes connection, and we must consequently look still higher for this unity as qualitative (see Suppl. XII. § 12), in that, namely, which itself contains the ground for the unity of different concepts in judgments, that is, the ground for the very possibility of the understanding, even in its logical employment.

§ 16

The Original Synthetical Unity of Apperception

It must be possible that the I think should accompany all my representations: for otherwise something would be represented within me that could not be thought, in other words, the representation would either be impossible or nothing, at least so far as I am concerned. That representation which can be given before all thought, is called intuition, and all the manifold of intuition has therefore a necessary relation to the I think in the same subject in which that manifold of intuition is found. That representation, however (that I think), is an act of spontaneity, that is, it cannot be considered as belonging to sensibility. I call it pure apperception, in order to distinguish it from empirical apperception, or original apperception also, because it is that self-consciousness which by producing the representation, I think (which must accompany all others, and is one and the same in every act of consciousness), cannot itself be accompanied by any other. I also call the unity of it the transcendental unity of self-consciousness, in order to indicate that it contains the possibility of knowledge a priori.

For the manifold representations given in any intuition would not all be my representations, if they did not all belong to one self-consciousness. What I mean is that, as my representations (even though I am not conscious of them as such), they must be in accordance with that condition, under which alone they can stand together in one common self-consciousness, because otherwise they would not all belong to me. From this original connection the following important conclusions can be deduced.

The unbroken identity of apperception of the manifold that is given in intuition contains a synthesis of representations, and is possible only through the consciousness of that synthesis. The empirical consciousness, which accompanies various representations, is itself various and disunited, and without reference to the identity of the subject. Such a relation takes place, not by my simply accompanying every relation with consciousness, but by my adding one to the other and being conscious of that act of adding, that is, of that synthesis. Only because I am able to connect the manifold of given representations in one consciousness, is it possible for me to represent to myself the identity of the consciousness in these representations, that is, only under the supposition of some synthetical unity of apperception does the analytical unity of apperception become possible.1

The thought that the representations given in intuition belong all of them to me, is therefore the same as that I connect them in one self-consciousness, or am able at least to do so; and though this is not yet the consciousness of the synthesis of representations, it nevertheless presupposes the possibility of this synthesis. In other words, it is only because I am able to comprehend the manifold of representations in one consciousness, that I call them altogether my representations, for otherwise, I should have as manifold and various a self as I have representations of which I am conscious. The synthetical unity of the manifold of intuitions as given a priori is therefore the ground also of the identity of that apperception itself which precedes a priori all definite thought. Connection, however, does never lie in the objects, and cannot be borrowed from them by perception, and thus be taken into the understanding, but it is always an act of the understanding, which itself is nothing but a faculty of connecting a priori, and of bringing the manifold of given representations under the unity of apperception, which is, in fact, the highest principle of all human knowledge.

It is true, no doubt, that this principle of the necessary unity of apperception is itself identical, and therefore an analytical proposition; but it shows, nevertheless, the necessity of a synthesis of the manifold which is given in intuition, without which synthesis it would be impossible to think the unbroken identity of self-consciousness. For through the Ego, as a simple representation, nothing manifold is given; in the intuition, which is different from that, it can be given only, and then, by connection, be thought in one consciousness. An understanding in which, by its self-consciousness, all the manifold would be given at the same time, would possess intuition; our understanding can do nothing but think, and must seek for its intuition in the senses. I am conscious, therefore, of the identical self with respect to the manifold of the representations, which are given to me in an intuition, because I call them, altogether, my representations, as constituting one. This means, that I am conscious of a necessary synthesis of them a priori, which is called the original synthetical unity of apperception under which all representations given to me must stand, but have to be brought there, first, by means of a synthesis.

§ 17

The Principle of the Synthetical Unity of Apperception is the Highest Principle of all Employment of the Understanding

The highest principle of the possibility of all intuition, in relation to sensibility, was, according to the transcendental Æsthetic, that all the manifold in it should be subject to the formal conditions of space and time. The highest principle of the same possibility in relation to the understanding is, that all the manifold in intuition must be subject to the conditions of the original synthetical unity of apperception.1

All the manifold representations of intuition, so far as they are given us, are subject to the former, so far as they must admit of being connected in one consciousness, to the latter; and without that nothing can be thought or known by them, because the given representations would not share the act of apperception (I think) in common, and could not be comprehended in one self-consciousness.

The understanding in its most general sense is the faculty of cognitions. These consist in a definite relation of given representations to an object; and an object is that in the concept of which the manifold of a given intuition is connected. All such connection of representations requires of course the unity of the consciousness in their synthesis: consequently, the unity of consciousness is that which alone constitutes the relation of representations to an object, that is, their objective validity, and consequently their becoming cognitions, so that the very possibility of the understanding depends on it.

The first pure cognition of the understanding, therefore, on which all the rest of its employment is founded, and which at the same time is entirely independent of all conditions of sensuous intuition, is this very principle of the original synthetical unity of apperception. Space, the mere form of external sensuous intuition, is not yet cognition: it only supplies the manifold of intuition a priori for a possible cognition. In order to know anything in space, for instance, a line, I must draw it, and produce synthetically a certain connection of the manifold that is given, so that the unity of that act is at the same time the unity of the consciousness (in the concept of a line), and (so that) an object (a determinate space) is then only known for the first time. The synthetical unity of consciousness is, therefore, an objective condition of all knowledge; a condition, not necessary for myself only, in order to know an object, but one to which each intuition must be subject, in order to become an object for me, because the manifold could not become connected in one consciousness in any other way, and without such a synthesis.

No doubt, that proposition, as I said before, is itself analytical, though it makes synthetical unity a condition of all thought, for it really says no more than that all my representations in any given intuition must be subject to the condition under which alone I can ascribe them, as my representations, to the identical self, and therefore comprehend them, as synthetically connected, in one apperception through the general expression, I think.

And yet this need not be a principle for every possible understanding, but only for that which gives nothing manifold through its pure apperception in the representation, I am. An understanding which through its self-consciousness could give the manifold of intuition, and by whose representation the objects of that representation should at the same time exist, would not require a special act of the synthesis of the manifold for the unity of its consciousness, while the human understanding, which possesses the power of thought only, but not of intuition, requires such an act. To the human understanding that first principle is so indispensable that it really cannot form the least concept of any other possible understanding, whether it be intuitive by itself, or possessed of a sensuous intuition, different from that in space and time.

§ 18

What is the Objective Unity of Self-consciousness?

The transcendental unity of apperception connects all the manifold given in an intuition into a concept of an object. It is therefore called objective, and must be distinguished from the subjective unity of consciousness, which is a form of the internal sense, by which the manifold of intuition is empirically given, to be thus connected. Whether I can become empirically conscious of the manifold, as either simultaneous or successive, depends on circumstances, or empirical conditions. The empirical unity of consciousness, therefore, through the association of representations, is itself phenomenal and wholly contingent, while the pure form of intuition in time, merely as general intuition containing the manifold that is given, is subject to the original unity of the consciousness, through the necessary relation only of the manifold of intuition to the one, I think, — that is, through the pure synthesis of the understanding, which forms the a priori ground of the empirical synthesis. That unity alone is, therefore, valid objectively; the empirical unity of apperception, which we do not consider here, and which is only derived from the former, under given conditions in concreto, has subjective validity only. One man connects the representation of a word with one thing, another with another, and the unity of consciousness, with regard to what is empirical, is not necessary nor universally valid with reference to that which is given.

§ 19

The Logical Form of all Judgments consists in the Objective Unity of Apperception of the Concepts contained therein

I could never feel satisfied with the definition of a judgment in general, given by our logicians, who say that it is the representation of a relation between two concepts. Without disputing with them in this place as to the defect of that explanation, that it may possibly apply to categorical, but not to hypothetical and disjunctive judgments (the latter containing, not a relation of concepts, but of judgments themselves), — though many tedious consequences have arisen from this mistake of logicians, — I must at least make this observation, that we are not told in what that relation consists.1

But, if I examine more closely the relation of given cognitions in every judgment, and distinguish it, as belonging to the understanding, from the relation according to the rules of reproductive imagination (which has subjective validity only), I find that a judgment is nothing but the mode of bringing given cognitions into the objective unity of apperception. This is what is intended by the copula is, which is meant to distinguish the objective unity of given representations from the subjective. It (the copula is) indicates their relation to the original apperception, and their necessary unity, even though the judgment itself be empirical, and therefore contingent; as, for instance, bodies are heavy. By this I do not mean to say that these representations belong necessarily to each other, in the empirical intuition, but that they belong to each other by means of the necessary unity of apperception in the synthesis of intuitions, that is, according to the principles of the objective determination of all representations, so far as any cognition is to arise from them, these principles being all derived from the principle of the transcendental unity of apperception. Thus, and thus alone, does the relation become a judgment, that is, a relation that is valid objectively, and can thus be kept sufficiently distinct from the relation of the same representations, if it has subjective validity only, for instance, according to the laws of association. In the latter case, I could only say, that if I carry a body I feel the pressure of its weight, but not, that it, the body, is heavy, which is meant to say that these two representations are connected together in the object, whatever the state of the subject may be, and not only associated or conjoined in the perception, however often it may be repeated.

§ 20

All Sensuous Intuitions are subject to the Categories as to Conditions under which alone their Manifold Contents can come together in one Consciousness

The manifold which is given us in a sensuous intuition is necessarily subject to the original synthetical unity of apperception, because by it alone the unity of intuition becomes possible (§ 7). That act of the understanding, further, by which the manifold of given representations (whether intuitions or concepts) is brought under one apperception in general, is the logical function of a judgment (§ 19). The manifold, therefore, so far as it is given in an empirical intuition, is determined with regard to one of the logical functions of judgment, by which, indeed, it is brought to consciousness in general. The categories, however, are nothing but these functions of judgment, so far as the manifold of a given intuition is determined with respect to them (§ 13, see p. 84). Therefore the manifold in any given intuition is naturally subject to the categories.

§ 21

Note

The manifold, contained in an intuition which I call my own, is represented through the synthesis of the understanding, as belonging to the necessary unity of self-consciousness, and this takes place through the category.1

This category indicates, therefore, that the empirical consciousness of the manifold, given in any intuition, is subject to a pure self-consciousness a priori, in the same manner as the empirical intuition is subject to a pure sensuous intuition which likewise takes place a priori.

In the above proposition a beginning is made of a deduction of the pure concepts of the understanding. In this deduction, as the categories arise in the understanding only, independent of all sensibility, I ought not yet to take any account of the manner in which the manifold is given for an empirical intuition, but attend exclusively to the unity which, by means of the category, enters into the intuition through the understanding. In what follows (§ 26) we shall show, from the manner in which the empirical intuition is given in sensibility, that its unity is no other than that which is prescribed by the category (according to § 20) to the manifold of any given intuition. Thus only, that is, by showing their validity a priori with respect to all objects of our senses, the purpose of our deduction will be fully attained.

There is one thing, however, of which, in the above demonstration, I could not make abstraction: namely, that the manifold for an intuition must be given antecedently to the synthesis of the understanding, and independently of it; — how, remains uncertain. For if I were to imagine an understanding, itself intuitive (for instance, a divine understanding, which should not represent to itself given objects, but produce them at once by his representation), the categories would have no meaning with respect to such cognition. They are merely rules for an understanding whose whole power consists in thinking, that is, in the act of bringing the synthesis of the manifold, which is given to it in intuition from elsewhere, to the unity of apperception; an understanding which therefore knows nothing by itself, but connects only and arranges the material for cognition, that is, the intuition which must be given to it by the object. This peculiarity of our understanding of producing unity of apperception a priori by means of the categories only, and again by such and so many, cannot be further explained, any more than why we have these and no other functions of judgment, and why time and space are the only forms of a possible intuition for us.

§ 22

The Category admits of no other Employment for the Cognition of Things, but its Application to Objects of Experience

We have seen that to think an object is not the same as to know an object. In order to know an object, we must have the concept by which any object is thought (the category), and likewise the intuition by which it is given. If no corresponding intuition could be given to a concept, it would still be a thought, so far as its form is concerned: but it would be without an object, and no knowledge of anything would be possible by it, because, so far as I know, there would be nothing, and there could be nothing, to which my thought could be referred. Now the only possible intuition for us is sensuous (see Æsthetic); the thought of any object, therefore, by means of a pure concept of the understanding, can with us become knowledge only, if it is referred to objects of the senses. Sensuous intuition is either pure (space and time), or empirical, i.e. if it is an intuition of that which is represented in space and time, through sensation as immediately real. By means of pure intuition we can gain knowledge a priori of things as phenomena (in mathematics), but only so far as their form is concerned; but whether there are things which must be perceived, according to that form, remains unsettled. Mathematical concepts, by themselves, therefore, are not yet knowledge, except under the supposition that there are things which admit of being represented by us, according to the form of that pure sensuous intuition only. Consequently, as things in space and time are only given as perceptions (as representations accompanied by sensations), that is, through empirical representations, the pure concepts of the understanding, even if applied to intuitions a priori, as in mathematics, give us knowledge in so far only as these pure intuitions, and therefore through them the concepts of the understanding also, can be applied to empirical intuitions. Consequently the categories, by means of intuition, do not give us any knowledge of things, except under the supposition of their possible application to empirical intuition; they serve, in short, for the possibility of empirical knowledge only, which is called experience. From this it follows that the categories admit of no other employment for the cognition of things, except so far only as these are taken as objects of possible experience.

§ 23

The foregoing proposition is of the greatest importance, for it determines the limits of the employment of the pure concepts of the understanding with reference to objects, in the same manner as the transcendental Æsthetic determined the limits of the employment of the pure form of our sensuous intuition. Space and time are conditions of the possibility of how objects can be given to us, so far only as objects of the senses, therefore of experience, are concerned. Beyond these limits they represent nothing, for they belong only to the senses, and have no reality beyond them. Pure concepts of the understanding are free from this limitation, and extend to objects of intuition in general, whether that intuition be like our own or not, if only it is sensuous and not intellectual. This further extension, however, of concepts beyond our sensuous intuition, is of no avail to us; for they are in that case empty concepts of objects, and the concepts do not even enable us to say, whether such objects be possible or not. They are mere forms of thought, without objective reality: because we have no intuition at hand to which the synthetical unity of apperception, which is contained in the concepts alone, could be applied, so that they might determine an object. Nothing can give them sense and meaning, except our sensuous and empirical intuition.

If, therefore, we assume an object of a non-sensuous intuition as given, we may, no doubt, determine it through all the predicates, which follow from the supposition that nothing belonging to sensuous intuition belongs to it, that, therefore, it is not extended, or not in space, that its duration is not time, that no change (succession of determinations in time) is to be met in it, etc. But we can hardly call this knowledge, if we only indicate how the intuition of an object is not, without being able to say what is contained in it, for, in that case, I have not represented the possibility of an object, corresponding to my pure concept of the understanding, because I could give no intuition corresponding to it, but could only say that our intuition did not apply to it. But what is the most important is this, that not even a single category could be applied to such a thing; as, for instance, the concept of substance, that is, of something that can exist as a subject only, but never as a mere predicate. For I do not know whether there can be anything corresponding to such a determination of thought, unless empirical intuition supplies the case for its application. Of this more hereafter.

§ 24

Of the Application of the Categories to Objects of the Senses in General

The pure concepts of the understanding refer, through the mere understanding, to objects of intuition, whether it be our own, or any other, if only sensuous intuition, but they are, for that very reason, mere forms of thought, by which no definite object can be known. The synthesis, or connection of the manifold in them, referred only to the unity of apperception, and became thus the ground of the possibility of knowledge a priori, so far as it rests on the understanding, and is therefore not only transcendental, but also purely intellectual. Now as there exists in us a certain form of sensuous intuition a priori, which rests on the receptivity of the faculty of representation (sensibility), the understanding, as spontaneity, is able to determine the internal sense through the manifold of given representations, according to the synthetical unity of apperception, and can thus think synthetical unity of the apperception of the manifold of sensuous intuition a priori, as the condition to which all objects of our (human) intuition must necessarily be subject. Thus the categories, though pure forms of thought, receive objective reality, that is, application to objects which can be given to us in intuition, but as phenomena only; for it is with reference to them alone that we are capable of intuition a priori.

This synthesis of the manifold of sensuous intuition, which is possible and necessary a priori, may be called figurative (synthesis speciosa), in order to distinguish it from that which is thought in the mere category, with reference to the manifold of an intuition in general, and is called intellectual synthesis (synthesis intellectualis). Both are transcendental, not only because they themselves are carried out a priori, but because they establish also the possibility of other knowledge a priori.

But this figurative synthesis, if it refers to the original synthetical unity of apperception only, that is, to that transcendental unity which is thought in the categories, must be called the transcendental synthesis of the faculty of imagination, in order thus to distinguish it from the purely intellectual synthesis. Imagination is the faculty of representing an object even without its presence in intuition. As all our intuition is sensuous, the faculty of imagination belongs, on account of the subjective condition under which alone it can give a corresponding intuition to the concepts of the understanding, to our sensibility. As, however, its synthesis is an act of spontaneity, determining, and not, like the senses, determinable only, and therefore able to determine a priori the senses, so far as their form is concerned, according to the unity of apperception, the faculty of imagination is, so far, a faculty of determining our sensibility a priori, so that the synthesis of the intuitions, according to the categories, must be the transcendental synthesis of the faculty of imagination. This is an effect, produced by the understanding on our sensibility, and the first application of it (and at the same time the ground of all others) to objects of the intuition which is only possible to us. As figurative, it is distinguished from the intellectual synthesis, which takes place by the understanding only, without the aid of the faculty of imagination. In so far as imagination is spontaneity, I call it occasionally productive imagination: distinguishing it from the reproductive, which in its synthesis is subject to empirical laws only, namely, those of association, and which is of no help for the explanation of the possibility of knowledge a priori, belonging, therefore, to psychology, and not to transcendental philosophy.

*     *     *     *     *     *     *     *

This is the proper place for trying to account for the paradox, which must have struck everybody in our exposition of the form of the internal sense (§ 6, see p. 28); namely, how that sense represents to the consciousness even ourselves, not as we are by ourselves, but as we appear to ourselves, because we perceive ourselves only as we are affected internally. This seems to be contradictory, because we should thus be in a passive relation to ourselves; and for this reason the founders of the systems of psychology have preferred to represent the internal sense as identical with the faculty of apperception, while we have carefully distinguished the two.

What determines the internal sense is the understanding, and its original power of connecting the manifold of intuition, that is, of bringing it under one apperception, this being the very ground of the possibility of the understanding. As in us men the understanding is not itself an intuitive faculty, and could not, even if intuitions were given in our sensibility, take them into itself, in order to connect, as it were, the manifold of its own intuition, the synthesis of the understanding, if considered by itself alone, is nothing but the unity of action, of which it is conscious without sensibility also, but through which the understanding is able to determine that sensibility internally, with respect to the manifold which may be given to it (the understanding) according to the form of its intuition. The understanding, therefore, exercises its activity, under the name of a transcendental synthesis of the faculty of imagination, on the passive subject to which it belongs as a faculty, and we are right in saying that the internal sense is affected by that activity. The apperception with its synthetical unity is so far from being identical with the internal sense, that, as the source of all synthesis, it rather applies, under the name of the categories, to the manifold of intuitions in general, that is, to objects in general before all sensuous intuition; while the internal sense, on the contrary, contains the mere form of intuition, but without any connection of the manifold in it, and therefore, as yet, no definite intuition, which becomes possible only through the consciousness of the determination of the internal sense by the transcendental act of the faculty of imagination (the synthetical influence of the understanding on the internal sense) which I have called the figurative synthesis.

This we can always perceive in ourselves. We cannot think a line without drawing it in thought; we cannot think a circle without describing it; we cannot represent, at all, the three dimensions of space, without placing, from the same point, three lines perpendicularly on each other; nay, we cannot even represent time, except by attending, during our drawing a straight line (which is meant to be the external figurative representation of time) to the act of the synthesis of the manifold only by which we successively determine the internal sense, and thereby to the succession of that determination in it. It is really motion, as the act of the subject (not as the determination of an object1 ), therefore the synthesis of the manifold in space (abstraction being made of space, and our attention fixed on the act only by which we determine the internal sense, according to its form), which first produces the very concept of succession. The understanding does not, therefore, find in the internal sense such a connection of the manifold, but produces it by affecting the internal sense. It may seem difficult to understand how the thinking ego can be different from the ego which sees or perceives itself (other modes of intuition being at least conceivable), and yet identical with the latter as the same subject, and how, therefore, I can say: I, as intelligence and thinking subject, know myself as an object thought so far as being given to myself in intuition also, but like other phenomena, not as I am to the understanding, but only as I appear to myself. In reality, however, this is neither more nor less difficult than how I can be, to myself, an object, and, more especially, an object of intuition and of internal perceptions. But that this must really be so, can clearly be shown — if only we admit space to be merely a pure form of the phenomena of the external senses — by the fact that we cannot represent to ourselves time, which is no object of external intuition, in any other way than under the image of a line which we draw, a mode of representation without which we could not realise the unity of its dimension; or again by this other fact that we must always derive the determination of the length of time, or of points of time for all our internal perceptions, from that which is represented to us as changeable by external things, and have therefore to arrange the determinations of the internal sense as phenomena in time, in exactly the same way in which we arrange the determinations of the external senses in space. If, then, with regard to the latter, we admit that by them we know objects so far only as we are affected externally, we must also admit, with regard to the internal sense, that by it we only are, or perceive ourselves, as we are internally affected by ourselves, in other words, that with regard to internal intuition we know our own self as a phenomenon only, and not as it is by itself.1

§ 25

In the transcendental synthesis, however, of the manifold of representations in general, and therefore in the original synthetical unity of apperception, I am conscious of myself, neither as I appear to myself, nor as I am by myself, but only that I am. This representation is an act of thought, not of intuition. Now, in order to know ourselves, we require, besides the act of thinking, which brings the manifold of every possible intuition to the unity of apperception, a definite kind of intuition also by which that manifold is given, and thus, though my own existence is not phenomenal (much less a mere illusion), yet the determination of my existence2 can only take place according to the form of the internal sense, and in that special manner in which the manifold, which I connect, is given in the internal intuition. This shows that I have no knowledge of myself as I am, but only as I appear to myself. The consciousness of oneself is therefore very far from being a knowledge of oneself, in spite of all the categories which constitute the thinking of an object in general, by means of the connection of the manifold in an apperception. As for the knowledge of an object different from myself I require, besides the thinking of an object in general (in a category), an intuition also, to determine that general concept, I require for the knowledge of my own self, besides consciousness, or besides my thinking myself, an intuition also of the manifold in me, to determine that thought. I exist, therefore, as such an intelligence, which is simply conscious of its power of connection, but with respect to the manifold that has to be connected, is subject to a limiting condition which is called the internal sense, according to which that connection can only become perceptible in relations of time, which lie entirely outside the concepts of the understanding. Such an intelligence, therefore, can only know itself as it appears to itself in an intuition (which cannot be intellectual and given by the understanding itself), and not as it would know itself, if its intuition were intellectual.

§ 26

Transcendental Deduction of the Universally Possible Employment of the Pure Concepts of the Understanding in Experience

In the metaphysical deduction of the categories their a priori origin was proved by their complete accordance with the general logical functions of thought, while in their transcendental deduction we established their possibility as knowledge a priori of objects of an intuition in general (§ 20, 21). Now we have to explain the possibility of our knowing a priori, by means of the categories, whatever objects may come before our senses, and this not according to the form of their intuition, but according to the laws of their connection, and of our thus, as it were, prescribing laws to nature, nay, making nature possible. Unless they were adequate to that purpose, we could not understand how everything that may come before our senses must be subject to laws which have their origin a priori in the understanding alone.

First of all, I observe that by the synthesis of apprehension I understand the connection of the manifold in an empirical intuition, by which perception, that is, empirical consciousness of it (as phenomenal), becomes possible.

We have forms of the external as well as the internal intuition a priori, in our representations of space and time: and to these the synthesis of the apprehension of the manifold in phenomena must always conform, because it can take place according to that form only. Time and space, however, are represented a priori, not only as forms of sensuous intuition, but as intuitions themselves (containing a manifold), and therefore with the determination of the unity of that manifold in them (see transcendental Æsthetic1 ). Therefore unity of the synthesis of the manifold without or within us, and consequently a connection to which everything that is to be represented as determined in space and time must conform, is given a priori as the condition of the synthesis of all apprehension simultaneously with the intuitions, not in them, and that synthetical unity can be no other but that of the connection of the manifold of any intuition whatsoever in an original consciousness, according to the categories, only applied to our sensuous intuition. Consequently, all synthesis, without which even perception would be impossible, is subject to the categories; and as experience consists of knowledge by means of connected perceptions, the categories are conditions of the possibility of experience, and valid therefore a priori also for all objects of experience.

*     *     *     *     *     *     *     *

If, for instance, I raise the empirical intuition of a house, through the apprehension of the manifold contained therein, into a perception, the necessary unity of space and of external sensuous intuition in general is presupposed, and I draw, as it were, the shape of the house according to that synthetical unity of the manifold in space. But this very synthetical unity, if I make abstraction of the form of space, has its seat in the understanding, and is in fact the category of the synthesis of the homogeneous in intuition in general; that is, the category of quantity, to which that synthesis of apprehension, that is, the perception, must always conform.1

Or if, to take another example, I perceive the freezing of water, I apprehend two states (that of fluidity and that of solidity), and these as standing to each other in a relation of time. But in the time, which as internal intuition I make the foundation of the phenomenon, I represent to myself necessarily synthetical unity of the manifold, without which that relation could not be given as determined in an intuition (with reference to the succession of time). That synthetical unity, however, as a condition a priori, under which I connect the manifold of any intuition, turns out to be, if I make abstraction of the permanent form of my intuition, namely, of time, the category of cause, through which, if I apply it to my sensibility, I determine everything that happens, according to its relation in time. Thus the apprehension in such an event, and that event itself considered as a possible perception, is subject to the concept of the relation of cause and effect. The same applies to all other cases.

*     *     *     *     *     *     *     *

Categories are concepts which a priori prescribe laws to all phenomena, and therefore to nature as the sum total of all phenomena (natura materialiter spectata). The question therefore arises, as these laws are not derived from nature, nor conform to it as their model (in which case they would be empirical only), how we can understand that nature should conform to them, that is, how they can determine a priori the connection of the manifold in nature, without taking that connection from nature. The solution of that riddle is this.

It is no more surprising that the laws of phenomena in nature must agree with the understanding and its form a priori, that is, with its power of connecting the manifold in general, than that the phenomena themselves must agree with the form of sensuous intuition a priori. For laws exist as little in phenomena themselves, but relatively only, with respect to the subject to which, so far as it has understanding, the phenomena belong, as phenomena exist by themselves, but relatively only, with respect to the same being so far as it has senses. Things by themselves would necessarily possess their conformity to the law, independent also of any understanding by which they are known. But phenomena are only representations of things, unknown as to what they may be by themselves. As mere representations they are subject to no law of connection, except that which is prescribed by the connecting faculty. Now that which connects the manifold of sensuous intuition is the faculty of imagination, which receives from the understanding the unity of its intellectual synthesis, and from sensibility the manifoldness of apprehension. Thus, as all possible perceptions depend on the synthesis of apprehension, and that synthesis itself, that empirical synthesis, depends on the transcendental, and, therefore, on the categories, it follows that all possible perceptions, everything in fact that can come to the empirical consciousness, that is, all phenomena of nature, must, so far as their connection is concerned, be subject to the categories. On these categories, therefore, nature (considered as nature in general) depends, as on the original ground of its necessary conformity to law (as natura formaliter spectata). Beyond the laws, on which nature in general, as a lawful order of phenomena in space and time depends, the pure faculty of the understanding is incapable of prescribing a priori, by means of mere categories, laws to phenomena. Special laws, therefore, as they refer to phenomena which are empirically determined, cannot be completely derived from the categories, although they are all subject to them. Experience must be superadded in order to know such special laws: while those other a priori laws inform us only with regard to experience in general, and what can be known as an object of it.

§ 27

Results of this Deduction of the Concepts of the Understanding

We cannot think any object except by means of the categories; we cannot know any subject that has been thought, except by means of intuitions, corresponding to those concepts. Now all our intuitions are sensuous, and this knowledge, so far as its object is given, is empirical. But empirical knowledge is experience, and therefore no knowledge a priori is possible to us, except of objects of possible experience only.1

This knowledge, however, though limited to objects of experience, is not, therefore, entirely derived from experience, for both the pure intuitions and the pure concepts of the understanding are elements of knowledge which exist in us a priori. Now there are only two ways in which a necessary harmony of experience with the concepts of its objects can be conceived; either experience makes these concepts possible, or these concepts make experience possible. The former will not hold good with respect to the categories (nor with pure sensuous intuition), for they are concepts a priori, and therefore independent of experience. To ascribe to them an empirical origin, would be to admit a kind of generatio aequivoca. There remains, therefore, the second alternative only (a kind of system of the epigenesis of pure reason), namely, that the categories, on the part of the understanding, contain the grounds of the possibility of all experience in general. How they render experience possible, and what principles of the possibility of experience they supply in their employment on phenomena, will be shown more fully in the following chapter on the transcendental employment of the faculty of judgment.

Some one might propose to adopt a middle way between the two, namely, that the categories are neither self-produced first principles a priori of our knowledge, nor derived from experience, but subjective dispositions of thought, implanted in us with our existence, and so arranged by our Creator that their employment should accurately agree with the laws of nature, which determine experience (a kind of system of preformation of pure reason). But, in that case, not only would there be no end of such an hypothesis, so that no one could know how far the supposition of predetermined dispositions to future judgments might be carried, but there is this decided objection against that middle course that, by adopting it, the categories would lose that necessity which is essential to them. Thus the concept of cause, which asserts, under a presupposed condition, the necessity of an effect, would become false, if it rested only on some subjective necessity implanted in us of connecting certain empirical representations according to the rule of causal relation. I should not be able to say that the effect is connected with the cause in the object (that is, by necessity), but only, I am so constituted that I cannot think these representations as connected in any other way. This is exactly what the sceptic most desires, for in that case all our knowledge, resting on the supposed objective validity of our judgments, is nothing but mere illusion, nor would there be wanting people to say they know nothing of such subjective necessity (which can only be felt); and at all events we could not quarrel with anybody about what depends only on the manner in which his own subject is organised.

Comprehensive View of this Deduction

The deduction of the pure concepts of the understanding (and with them of all theoretical knowledge a priori) consists in representing them as principles of the possibility of experience, and in representing experience as the determination of phenomena in space and time, — and, lastly, in representing that determination as depending on the principle of the original synthetical unity of apperception, as the form of the understanding, applied to space and time, as the original forms of sensibility.1

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SUPPLEMENT XV

[See page 132]

All conjunction (conjunctio) is either composition (compositio) or connection (nexus). The former is the synthesis of a manifold the parts of which do not belong to each other necessarily. The two triangles, for instance, into which a square is divided by a diagonal, do by themselves not necessarily belong to each other. Such is also the synthesis of the homogeneous, in everything that can be considered mathematically, and that synthesis can be divided again into aggregation, and coalition, the former referring to extensive, the latter to intensive qualities. The latter conjunction (nexus) is the synthesis of a manifold, in so far as its elements belong to each other necessarily. Thus the accident belonging to a substance, or the effect belonging to a cause, though heterogeneous, are yet represented as a priori connected, which connection, as it is not arbitrary, I call dynamical, because it concerns the connection of the existence of the manifold. This may again be divided into the physical connection of phenomena among each other, and their metaphysical connection in the faculty of cognition a priori. (This forms a note in the 2nd Edition.)

SUPPLEMENT XVI a

[See page 133]

In the 2nd Edition the title is

I

Axioms of Intuition

Their principle is: All intuitions are extensive quantities.

Proof

All phenomena contain, so far as their form is concerned, an intuition in space and time, which forms the a priori foundation of all of them. They cannot, therefore, be apprehended, that is, received into empirical consciousness, except through the synthesis of the manifold, by which the representations of a definite space or time are produced, i.e. through the synthesis of the homogeneous, and the consciousness of the synthetical unity of that manifold (homogeneous). Now the consciousness of the manifold and homogeneous in intuition, so far as by it the representation of an object is first rendered possible, is the concept of quantity (quantum). Therefore even the perception of an object as a phenomenon is possible only through the same synthetical unity of the manifold of the given sensuous intuition, by which the unity of the composition of the manifold and homogeneous is conceived in the concept of a quantity; that is, phenomena are always quantities, and extensive quantities; because as intuitions in space and time, they must be represented through the same synthesis through which space and time in general are determined.

SUPPLEMENT XVI b

[See page 136]

II

Anticipations of Perception

Their principle is: In all phenomena the Real, which is the object of a sensation, has intensive quantity, that is, a degree.

Proof

Perception is empirical consciousness, that is, a consciousness in which there is at the same time sensation. Phenomena, as objects of perception, are not pure (merely formal) intuitions, like space and time (for space and time can never be perceived by themselves). They contain, therefore, over and above the intuition, the material for some one object in general (through which something existing in space and time is represented); that is, they contain the real of sensation, as a merely subjective representation, which gives us only the consciousness that the subject is affected, and which is referred to some object in general. Now there is a gradual transition possible from empirical to pure consciousness, till the real of it vanishes completely and there remains a merely formal consciousness (a priori) of the manifold in space and time; and, therefore, a synthesis also is possible in the production of the quantity of a sensation, from its beginning, that is, from the pure intuition = 0, onwards to any quantity of it. As sensation by itself is no objective representation, and as in it the intuition of neither space nor time can be found, it follows that though not an extensive, yet some kind of quantity must belong to it (and this through the apprehension of it, in which the empirical consciousness may grow in a certain time from nothing = 0 to any amount). That quantity must be intensive, and corresponding to it, an intensive quantity, i.e. a degree of influence upon the senses, must be attributed to all objects of perception, so far as it contains sensation.

SUPPLEMENT XVII

[See page 144]

III

Analogies of Experience

Their principle is: Experience is possible only through the representation of a necessary connection of perceptions.

Proof

Experience is empirical knowledge, that is, knowledge which determines an object by means of perceptions. It is, therefore, a synthesis of perceptions, which synthesis itself is not contained in the perception, but contains the synthetical unity of the manifold of the perceptions in a consciousness, that unity constituting the essential of our knowledge of the objects of the senses, i.e. of experience (not only of intuition or of sensation of the senses). In experience perceptions come together contingently only, so that no necessity of their connection could be discovered in the perceptions themselves, apprehension being only a composition of the manifold of empirical intuition, but containing no representation of the necessity of the connected existence, in space and time, of the phenomena which it places together. Experience, on the contrary, is a knowledge of objects by perceptions, in which therefore the relation in the existence of the manifold is to be represented, not as it is put together in time, but as it is in time, objectively. Now, as time itself cannot be perceived, the determination of the existence of objects in time can take place only by their connection in time in general, that is, through concepts connecting them a priori. As these concepts always imply necessity, we are justified in saying that experience is possible only through a representation of the necessary connection of perceptions.

SUPPLEMENT XVIII

[See page 149]

A. First Analogy

Principle of the Permanence of Substance

In all changes of phenomena the substance is permanent, and its quantum is neither increased nor diminished in nature.

Proof

All phenomena exist in time, and in it alone, as the substratum (as permanent form of the internal intuition), can simultaneousness as well as succession be represented. Time, therefore, in which all change of phenomena is to be thought, does not change, for it is that in which simultaneousness and succession can be represented only as determinations of it. As time by itself cannot be perceived, it follows that the substratum which represents time in general, and in which all change or simultaneousness can be perceived in apprehension, through the relation of phenomena to it, must exist in the objects of perception, that is, in the phenomena. Now the substratum of all that is real, that is, of all that belongs to the existence of things, is the substance, and all that belongs to existence can be conceived only as a determination of it. Consequently the permanent, in reference to which alone all temporal relations of phenomena can be determined, is the substance in phenomena, that is, what is real in them, and, as the substratum of all change, remains always the same. As therefore substance cannot change in existence, we were justified in saying that its quantum can neither be increased nor diminished in nature.

SUPPLEMENT XIX

[See page 155]

B. Second Analogy

Principle of the Succession of Time, according to the Law of Causality

All changes take place according to the law of connection between cause and effect.

Proof

(It has been shown by the preceding principle, that all phenomena in the succession of time are changes only, i.e. a successive being and not-being of the determinations of the substance, which is permanent, and consequently that the being of the substance itself, which follows upon its not-being, and its not-being, which follows on its being, — in other words, that an arising or perishing of the substance itself is inadmissible. The same principle might also have been expressed thus: all change (succession) of phenomena consists in modification only, for arising and perishing are no modifications of the substance, because the concept of modification presupposes the same subject as existing with two opposite determinations, and therefore as permanent. After this preliminary remark, we shall proceed to the proof.)

I perceive that phenomena succeed each other, that is, that there is a state of things at one time the opposite of which existed at a previous time. I am therefore really connecting two perceptions in time. That connection is not a work of the senses only and of intuition, but is here the product of a synthetical power of the faculty of imagination, which determines the internal sense with reference to relation in time. Imagination, however, can connect those two states in two ways, so that either the one or the other precedes in time: for time cannot be perceived by itself, nor can we determine in the object empirically and with reference to time, what precedes and what follows. I am, therefore, conscious only that my imagination places the one before, the other after, and not, that in the object the one state comes before the other. In other words, the objective relation of phenomena following upon each other remains undetermined by mere perception. In order that this may be known as determined, it is necessary to conceive the relation between the two states in such a way that it should be determined thereby with necessity, which of the two should be taken as coming first, and which as second, and not conversely. Such a concept, involving a necessity of synthetical unity, can be a pure concept of the understanding only, which is not supplied by experience, and this is, in this case, the concept of the relation of cause and effect, the former determining the latter in time as the consequence, the cause not being something that might be antecedent in imagination only, or might not be perceived at all. Experience itself, therefore, that is, an empirical knowledge of phenomena, is possible only by our subjecting the succession of phenomena, and with it all change, to the law of causality, and phenomena themselves, as objects of experience, are consequently possible according to the same law only.

SUPPLEMENT XX

[See page 172]

C. Third Analogy

Principle of Coexistence, according to the Law of Reciprocity or Community

All substances, so far as they can be perceived as coexistent in space, are always affecting each other reciprocally.

Proof

Things are coexistent when, in empirical intuition, the perception of the one can follow upon the perception of the other, and vice versa, which, as was shown in the second principle, is impossible in the temporal succession of phenomena. Thus I may first observe the moon and afterwards the earth, or, conversely also, first the earth and afterwards the moon, and because the perceptions of these objects can follow each other in both ways, I say that they are coexistent. Now coexistence is the existence of the manifold in the same time. Time itself, however, cannot be perceived, so that we might learn from the fact that things exist in the same time that their perceptions can follow each other reciprocally. The synthesis of imagination in apprehension would, therefore, give us each of these perceptions as existing in the subject, when the other is absent, and vice versa: it would never tell us that the objects are coexistent, that is, that if the one is there, the other also must be there in the same time, and this by necessity, so that the perceptions may follow each other reciprocally. Hence we require a concept of understanding of the reciprocal sequence of determinations of things existing at the same time, but outside each other, in order to be able to say, that the reciprocal sequence of the perceptions is founded in the object, and thus to represent their coexistence as objective. The relation of substances, however, of which the first has determinations the ground of which is contained in the other, is the relation of influence, and if, conversely also, the first contains the ground of determinations in the latter, the relation is that of community or reciprocity. Hence the coexistence of substances in space cannot be known in experience otherwise but under the supposition of reciprocal action: and this is therefore the condition also of the possibility of things themselves as objects of experience.

SUPPLEMENT XXI

[See page 184]

An important protest, however, against these rules for proving existence mediately is brought forward by Idealism, and this is therefore the proper place for its refutation.

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Refutation of Idealism

Idealism (I mean material idealism) is the theory which declares the existence of objects in space, without us, as either doubtful only and not demonstrable, or as false and impossible. The former is the problematical idealism of Descartes, who declares one empirical assertion only to be undoubted, namely, that of I am; the latter is the dogmatical idealism of Berkeley, who declares space and all things to which it belongs as an inseparable condition, as something impossible in itself, and, therefore, the things in space as mere imaginations. Dogmatic idealism is inevitable, if we look upon space as a property belonging to things by themselves, for in that case space and all of which it is a condition, would be a non-entity. The ground on which that idealism rests has been removed by us in the transcendental Æsthetic. Problematical idealism, which asserts nothing, but only pleads our inability of proving any existence except our own by means of immediate experience, is reasonable and in accordance with a sound philosophical mode of thought, which allows of no decisive judgment, before a sufficient proof has been found. The required proof will have to demonstrate that we may have not only an imagination, but also an experience of external things, and this it seems can hardly be effected in any other way except by proving that even our internal experience, which Descartes considers as andoubted, is possible only under the supposition of external experience.

Theorem

The simple, but empirically determined Consciousness of my own existence, proves the Existence of objects in space outside myself.

Proof

I am conscious of my own existence as determined in time, and all determination in time presupposes something permanent in the perception.1 That permanent, however, cannot be an intuition within me, because all the causes which determine my existence, so far as they can be found within me, are representations, and as such require themselves something permanent, different from them, in reference to which their change, and therefore my existence in time in which they change, may be determined. The perception of this permanent, therefore, is possible only through a thing outside me, and not through the mere representation of a thing outside me, and the determination of my existence in time is, consequently, possible only by the existence of real things, which I perceive outside me. Now, as the consciousness in time is necessarily connected with the consciousness of the possibility of that determination of time, it is also necessarily connected with the existence of things outside me, as the condition of the determination of time. In other words, the consciousness of my own existence is, at the same time, an immediate consciousness of the existence of other things.

Note 1. — It will have been perceived that in the foregoing proof the trick played by idealism has been turned against it, and with greater justice. Idealism assumed that the only immediate experience is the internal, and that from it we can no more than infer external things, though in an untrustworthy manner only, as always happens if from given effects we infer definite causes: it being quite possible that the cause of the representations, which are ascribed by us, it may be wrongly, to external things, may lie within ourselves. We, however, have proved that external experience is really immediate,1 and that only by means of it, though not the consciousness of our own existence, yet its determination in time, that is, internal experience, becomes possible. No doubt the representation of I am, which expresses the consciousness that can accompany all thought, is that which immediately includes the existence of a subject: but it does not yet include a knowledge of it, and therefore no empirical knowledge, that is, experience. For that we require, besides the thought of something existing, intuition also, and in this case internal intuition in respect to which, that is, to time, the subject must be determined. For that purpose external objects are absolutely necessary, so that internal experience itself is possible, mediately only, and through external experience.

Note 2. — This view is fully confirmed by the empirical use of our faculty of knowledge, as applied to the determination of time. Not only are we unable to perceive any determination of time, except through a change in external relations (motion) with reference to what is permanent in space (for instance, the movement of the sun with respect to terrestrial objects), but we really have nothing permanent to which we could refer the concept of a substance, as an intuition, except matter only: and even its permanence is not derived from external experience, but presupposed a priori as a necessary condition of all determination of time, and therefore also of1 the determination of the internal sense with respect to our own existence through the existence of external things. The consciousness of myself, in the representation of the ego, is not an intuition, but a merely intellectual representation of the spontaneity of a thinking subject. Hence that ego has not the slightest predicate derived from intuition, which predicate, as permanent, might serve as the correlate of the determination of time in the internal sense: such as is, for instance, impermeability in matter, as an empirical intuition.

Note 3. — Because the existence of external objects is required for the possibility of a definite consciousness of ourselves, it does not follow that every intuitional representation of external things involves, at the same time, their existence; for such a representation may well be the mere effect of the faculty of imagination (in dreams as well as in madness); but it can be such an effect only through the reproduction of former external perceptions, which, as we have shown, is impossible without the reality of external objects. What we wanted to prove here was only that internal experience in general is possible only through external experience in general. Whether this or that supposed experience be purely imaginary, must be settled according to its own particular determinations, and through a comparison with the criteria of all real experience.

SUPPLEMENT XXII

[See page 191]

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General Note on the System of the Principles

It is something very remarkable that we cannot understand the possibility of anything from the category alone, but must always have an intuition in order to exhibit by it the objective reality of the pure concept of the understanding. Let us take, for instance, the categories of relation. It is impossible to understand, from mere concepts alone: —

First, how something can exist as subject only, and not as a mere determination of other things, that is, how it can be a substance: or,

Secondly, how, because something is, something else must be, that is, how something can ever be a cause: or,

Thirdly, how, when there are several things, something could follow from the existence of one of them as affecting the rest, and vice versa, so that there should exist, in this way, a certain community of substances. The same applies to the other categories, as, for instance, how a thing could be of the same kind as many others, and thus be a quantity. So long as there is no intuition, we do not know whether by the categories we conceive an object, nay, whether any object can at all belong to them: and thus we see again that by themselves the categories are not knowledge, but mere forms of thought, by which given intuitions are turned into knowledge.

It likewise follows from this, that no synthetical proposition can be made out of mere categories, as, for instance, if it is said that in everything existing there is substance, i.e. something that can exist as subject only, and not as a mere predicate; or, everything is a quantum, etc. Here we have really nothing whatever which would enable us to go beyond a given concept, and to connect with it another. Hence no one has ever succeeded in proving a synthetical proposition by pure concepts of the understanding only: as, for instance, the proposition that everything which exists contingently, has a cause. All that could be proved was, that, without such a relation, we could not conceive the existence of what is contingent, that is, that we could not know a priori through the understanding the existence of such a thing; from which it does not follow in the least that the same condition applies to the possibility of things themselves. If the reader will go back to our proof of the principle of causality, he will perceive that we could prove it of objects of possible experience only, by saying that everything which happens (every event) presupposes a cause. We could prove it only as the principle of the possibility of experience, that is, of the knowledge of an object, given in empirical intuition, but not by means of mere concepts. It is perfectly true, that nevertheless this proposition, that everything contingent must have a cause, carries conviction to everybody from mere concepts: but it should be observed, that in this case the concept of the contingent contains no longer the category of modality (as something the non-existence of which can be conceived), but that of relation (as something which can only exist as the consequence of something else). It thus becomes in reality an identical proposition, namely, that that which can exist as a consequence only has its cause. And thus, when we have to give examples of contingent existence, we have always recourse to changes, and not only to the possibility of conceiving the opposite.1 Change, however, is an event which, as such, is possible through a cause only, and the non-existence of which is therefore possible in itself. We thus mean by contingency, that something can exist as the effect of a cause only; and if therefore a thing is assumed to be contingent, it becomes a merely analytical proposition to say that it has a cause.

It is still more remarkable, however, that, in order to understand the possibility of things according to the categories, and thus to establish the objective reality of the latter, we require not only intuitions, but always external intuitions. Thus, if we take, for instance, the pure concepts of relation, we find that: —

First, in order to give something permanent in intuition, corresponding to the concept of substance (and thus to show the objective reality of that concept), we require an intuition in space (of matter), because space alone can determine anything as permanent, while time, and therefore everything that exists in the internal sense, is in a constant flux.

Secondly, that in order to exhibit change, as the intuition corresponding to the concept of causality, we must use motion as change in space for our example, nay, can thus only gain an intuition of changes the possibility of which no pure understanding can ever conceive. Change is the connection of contradictory opposites in the existence of one and the same thing. Now, how it is possible that from a given state another state, opposed to it, should arise in the same thing, no reason can comprehend without an example; nay, without an intuition, cannot even render it intelligible to itself. That intuition, however, is that of the motion of a point in space, the presence of which in different places (as a consequence of opposite determinations) gives us, for the first time, an intuition of change: so that, in order to make even internal changes afterwards conceivable to ourselves, we must make time, as the form of the internal sense, figuratively comprehensible to ourselves by means of a line, and the internal change by means of the drawing of that line (motion): in other words, the successive existence of ourselves in different states, by means of an external intuition. The real reason of this lies in the fact that all change presupposes something permanent in intuition, in order that it may itself be perceived as change, while no permanent intuition is to be found in the internal sense.

Thirdly, and lastly, the category of community cannot, so far as its possibility is concerned, be conceived by mere reason alone: and the objective reality of that concept cannot therefore be possibly understood without intuition, and without external intuition in space. For how should we conceive the possibility that, when several substances exist, something (as an effect) could follow from the existence of one of them as affecting reciprocally the existence of the other, and that, therefore, because there is something in the former, something must also be in the latter, which, from the existence of the latter alone, could not be understood? For this is necessary to establish community, though it is utterly inconceivable among things, each of which completely isolates itself through its substantiality. Leibniz, therefore, as he attributed community to the substances of the world, as conceived by the understanding alone, required the interference of a Deity; because, as he justly perceived, such community would have been inconceivable from the existence of such substances only. We, on the contrary, can render the possibility of such a communion (of substances as phenomena) perfectly conceivable to ourselves, if we represent them to ourselves in space, that is, in external intuition. For space contains, even a priori, formal external relations, as conditions of the possibility of the real relations of action and reaction, that is, of community.

It is easy to show, in the same manner, that the possibility of things as quanta, and therefore, the objective reality of the category of quantity, can be exhibited in external intuition only, and, by means of it alone, be afterwards applied to the internal sense. But, in order to avoid prolixity, I must leave it to the reflection of the reader to find the examples of this.

The whole of these notes is of great importance, not only as confirming our previous refutation of idealism, but even more, when we come to treat of self-knowledge by mere internal consciousness, and the determination of our own nature, without the help of external empirical intuitions, in order to show us the limits of the possibility of such knowledge.

The last result of the whole of this section is therefore this: All principles of the pure understanding are nothing more than a priori principles of the possibility of experience; and to experience alone do all synthetical propositions a priori relate: nay, their possibility itself rests entirely on that relation.

SUPPLEMENT XXIII

[See page 199]

In one word, none of these concepts admit of being authenticated, nor can their real possibility be proved, if all sensuous intuition (the only one which we possess) is removed, and there remains in that case a logical possibility only, that is, that a concept (a thought) is possible. This, however, does not concern us here, but only whether the concept refers to an object and does therefore signify anything.

SUPPLEMENT XXIV

[See page 203]

We are met here by an illusion which is difficult to avoid. The categories do not depend in their origin on sensibility, like the forms of intuition, space, and time, and seem, therefore, to admit of an application extending beyond the objects of the senses. But, on the other side, they are nothing but forms of thought, containing the logical faculty only of comprehending a priori in one consciousness the manifold that is given in intuition, and they would therefore, if we take away the only intuition which is possible to us, have still less significance than those pure sensuous forms by which at least an object is given, while a peculiar mode of our understanding of connecting the manifold (unless that intuition, in which the manifold alone can be given, is added), signifies nothing at all.

Nevertheless, it seems to follow from our very concept, if we call certain objects, as phenomena, beings of the senses, by distinguishing between the mode of our intuition and the nature of those objects by themselves, that we may take either the same objects in that latter capacity, though they cannot as such come before our intuition, or other possible things, which are not objects of our senses at all, and place them, as objects thought only by the understanding, in opposition to the former, calling them beings of the understanding (noumena). The question then arises, whether our pure concepts of the understanding do not possess some significance with regard to these so-called beings of the understanding, and constitute a mode of knowing them?

At the very outset, however, we meet with an ambiguity which may cause great misapprehension. The understanding, by calling an object in one aspect a phenomenon only, makes to itself, apart from that aspect, another representation of an object by itself, and imagines itself able to form concepts of such an object. As, then, the understanding yields no other concepts but the categories, it supposes that the object in the latter aspect can be thought at least by those pure concepts of the understanding, and is thus induced to take the entirely indefinite concept of a being of the understanding, as of a something in general outside our sensibility, as a definite concept of a being which we might know to a certain extent through the understanding.

If by noumenon we mean a thing so far as it is not an object of our sensuous intuition, and make abstraction of our mode of intuition, it may be called a noumenon in a negative sense. If, however, we mean by it an object of a non-sensuous intuition, we admit thereby a peculiar mode of intuition, namely, the intellectual, which, however, is not our own, nor one of which we can understand even the possibility. This would be the noumenon in a positive sense.

The doctrine of sensibility is at the same time the doctrine of noumena in their negative sense; that is, of things which the understanding must think without reference to our mode of intuition, and therefore, not as phenomena only, but as things by themselves, but to which, after it has thus separated them, the understanding knows that it must not, in this new aspect, apply its categories; because these categories have significance only with reference to the unity of intuitions in space and time, and can therefore a priori determine that unity, on account of the mere ideality of space and time only, by means of general connecting concepts. Where that unity in time cannot be found, i.e. in the noumenon, the whole use, nay, the whole significance of categories comes to an end: because even the possibility of things that should correspond to the categories, would be unintelligible. On this point I may refer the reader to what I have said at the very beginning of the general note to the previous chapter (Suppl. XXII). The possibility of a thing can never be proved from the fact that its concept is not self-contradictory, but only by being authenticated by an intuition corresponding to it. If, therefore, we attempted to apply the categories to objects which are not considered as phenomena, we should have to admit an intuition other than the sensuous, and thus the object would become a noumenon in a positive sense. As, however, such an intuition, namely, an intellectual one, is entirely beyond our faculty of knowledge, the use of the categories also can never reach beyond the limits of the objects of experience. Beings of the understanding correspond no doubt to beings of the senses, and there may be beings of the understanding to which our faculty of sensuous intuition has no relation at all; but our concepts of the understanding, being forms of thought for our sensuous intuition only, do not reach so far, and what is called by us a noumenon must be understood as such in a negative sense only.

SUPPLEMENT XXV

[See page 209]

We must not speak, as is often done, of an intellectual world, for intellectual and sensitive apply to knowledge only. That, however, to which the one or the other mode of intuition applies, that is, the objects themselves, must, however harsh it may sound, be called intelligible or sensible.

SUPPLEMENT XXVI

[See page 274]

Metaphysic has for the real object of its investigations three ideas only, God, Freedom, and Immortality; the second concept connected with the first leading by necessity to the third as conclusion. Everything else treated by that science is a means only in order to establish those ideas and their reality. Metaphysic does not require these ideas for the sake of natural science; but in order to go beyond nature. A right insight into them would make theology, morality, and, by the union of both, religion also, therefore the highest objects of our existence, dependent on the speculative faculty of reason only, and on nothing else. In a systematical arrangement of those ideas the above order, being synthetical, would be the most appropriate; but in their elaboration, which must necessarily come first, the analytical or inverse order is more practical, enabling us, by starting from what is given us by experience, namely, the study of the soul (psychology), and proceeding thence to the study of the world (cosmology), and lastly, to a knowledge of God (theology), to carry out the whole of our great plan in its entirety.

SUPPLEMENT XXVII

[See page 284]

We shall therefore follow it with a critical eye through all the predicaments of pure psychology; but we shall, for the sake of brevity, let their examination proceed uninterruptedly.

The following general remark may at the very outset make us more attentive to this mode of syllogism. I do not know any object by merely thinking, but only by determining a given intuition with respect to that unity of consciousness in which all thought consists; therefore, I do not know myself by being conscious of myself, as thinking, but only if I am conscious of the intuition of myself as determined with respect to the function of thought. All modes of self-consciousness in thought are therefore by themselves not yet concepts of understanding of objects (categories), but mere logical functions, which present no object to our thought to be known, and therefore do not present myself either as an object. It is not a consciousness of the determining, but only that of the determinable self, that is, of my internal intuition (so far as the manifold in it can be connected in accordance with the general condition of the unity of apperception in thought) which forms the object.

1. In all judgments I am always the determining subject only of the relation which constitutes the judgment. That I, who think, can be considered in thinking as subject only, and as something not simply inherent in the thinking, as predicate, is an apodictical and even identical proposition; but it does not mean that, as an object, I am a self-dependent being or a substance. The latter would be saying a great deal, and requires for its support data which are not found in the thinking, perhaps (so far as I consider only the thinking subject as such) more than I shall ever find in it.

2. That the Ego of apperception, and therefore the Ego in every act of thought, is a singular which cannot be dissolved into a plurality of subjects, and that it therefore signifies a logically simple subject, follows from the very concept of thinking, and is consequently an analytical proposition. But this does not mean that a thinking Ego is a simple substance, which would indeed be a synthetical proposition. The concept of substance always relates to intuitions which, with me, cannot be other but sensuous, and which therefore lie completely outside the field of the understanding and its thinking, which alone is intended here, when we say that the Ego, in thinking, is simple. It would indeed be strange, if what elsewhere requires so great an effort, namely, to distinguish in what is given by intuition what is substance, and still more, whether that substance can be simple (as in the case of the component parts of matter), should in our case be given to us so readily in what is really the poorest of all representations, and, as it were, by an act of revelation.

3. The proposition of the identity of myself amidst the manifold of which I am conscious, likewise follows from the concepts themselves, and is therefore analytical; but the identity of the subject of which, in all its representations, I may become conscious, does not refer to the intuition by which it is given as an object, and cannot therefore signify the identity of the person, by which is understood the consciousness of the identity of one’s own substance, as a thinking being, in all the changes of circumstances. In order to prove this, the mere analysis of the proposition, I think, would avail nothing: but different synthetical judgments would be required, which are based on the given intuition.

4. To say that I distinguish my own existence, as that of a thinking being, from other things outside me (one of them being my body) is likewise an analytical proposition; for other things are things which I conceive as different from myself. But, whether such a consciousness of myself is even possible without things outside me, whereby representations are given to me, and whether I could exist merely as a thinking being (without being a man), I do not know at all by that proposition.

Nothing therefore is gained by the analysis of the consciousness of myself, in thought in general, towards the knowledge of myself as an object. The logical analysis of thinking in general is simply mistaken for a metaphysical determination of the object.

It would be a great, nay, even the only objection to the whole of our critique, if there were a possibility of proving a priori that all thinking beings are by themselves simple substances, that as such (as a consequence of the same argument) personality is inseparable from them, and that they are conscious of their existence as distinct from all matter. For we should thus have made a step beyond the world of sense and entered into the field of noumena, and after that no one could dare to question our right of advancing further, of settling in it, and, as each of us is favoured by luck, taking possession of it. The proposition that every thinking being is, as such, a simple substance, is synthetical a priori, because, first, it goes beyond the concept on which it rests, and adds to act of thinking in general the mode of existence; and secondly, because it adds to that concept a predicate (simplicity) which cannot be given in any experience. Hence synthetical propositions a priori would be not only admissible, as we maintained, in reference to objects of possible experience, and then only as principles of the possibility of that experience, but could be extended to things in general and to things by themselves, a result which would put an end to the whole of our critique, and bid us to leave everything as we found it. However, the danger is not so great, if only we look more closely into the matter.

In this process of rational psychology, there lurks a paralogism, which may be represented by the following syllogism.

That which cannot be conceived otherwise than as a subject, does not exist otherwise than as a subject, and is therefore a substance.

A thinking being, considered as such, cannot be conceived otherwise than as a subject.

Therefore it exists also as such only, that is, as a substance.

In the major they speak of a being that can be thought in every respect, and therefore also as it may be given in intuition. In the minor, however, they speak of it only so far as it considers itself, as subject, with respect to the thinking and the unity of consciousness only, but not at the same time in respect to the intuition whereby this unity is given as an object of thinking The conclusion, therefore, has been drawn by a sophism, and more especially by sophisma figurae dictionis.1

That we are perfectly right in thus resolving that famous argument into a paralogism, will be clearly seen by referring to the general note on the systematical representation of the principles, and to the section on the noumena, for it has been proved there that the concept of a thing, which can exist by itself as a subject, and not as a mere predicate, carries as yet no objective reality, that is, that we cannot know whether any object at all belongs to it, it being impossible for us to understand the possibility of such a mode of existence. It yields us therefore no knowledge at all. If such a concept is to indicate, under the name of a substance, an object that can be given, and thus become knowledge, it must be made to rest on a permanent intuition, as the indispensable condition of the objective reality of a concept, that is, as that by which alone the object can be given. In internal intuition, however, we have nothing permanent, for the Ego is only the consciousness of my thinking; and if we do not go beyond this thinking, we are without the necessary condition for applying the concept of substance, that is, of an independent subject, to the self, as a thinking being. Thus the simplicity of the substance entirely disappears with the objective reality of the concept: and is changed into a purely logical qualitative unity of self-consciousness in thinking in general, whether the subject be composite or not.

Refutation of Mendelssohn’s Proof of the Permanence of the Soul

This acute philosopher perceived very quickly how the ordinary argument that the soul (if it is once admitted to be a simple being) cannot cease to exist by decomposition, was insufficient to prove its necessary continuance, because it might cease to exist by simply vanishing. He therefore tried, in his Phædon, to prove that the soul was not liable to that kind of perishing which would be a real annihilation, by endeavouring to show that a simple being cannot cease to exist, because as it could not be diminished, and thus gradually lose something of its existence, and be changed, by little and little, into nothing (it having no parts, and therefore no plurality in itself), there could be no time between the one moment in which it exists, and the other in which it exists no longer; and this would be impossible.

He did not consider, however, that, though we might allow to the soul this simple nature, namely, that it contains nothing manifold, nothing by the side of each other, and therefore no extensive quantity, yet we could not deny to it, as little as to any other existing thing, intensive quantity, i.e. a degree of reality with respect to all its faculties, nay, to all which constitutes its existence. Such a degree of reality might diminish by an infinite number of smaller degrees, and thus the supposed substance (the thing, the permanence of which has not yet been established), might be changed into nothing, not indeed through decomposition, but through a gradual remission of its powers, or, if I may say so, through elanguescence. For even consciousness has always a degree, which admits of being diminished,1 and therefore also the faculty of being conscious of oneself, as well as all other faculties.

The permanence of the soul, therefore, considered merely as an object of the internal sense, remains undemonstrated and undemonstrable, though its permanence in life, while the thinking being (as man) is at the same time to itself an object of the external senses, is clear by itself. But this does not satisfy the rational psychologist, who undertakes to prove, from mere concepts, the absolute permanence of the soul, even beyond this life.1

If now we take the above propositions in synthetical connection, as indeed they must be taken, as valid for all thinking beings, in a system of rational psychology, and proceed from the category of relation, with the proposition, all thinking beings, as such, are substances, backwards through the series till the circle is completed, we arrive in the end at their existence, and this, according to that system, they are not only conscious of, independently of external things, but are supposed to be able to determine it even of themselves (with respect to that permanence which necessarily belongs to the character of substance). Hence it follows, that in this rationalistic system idealism is inevitable, at least problematical idealism, because, if the existence of external things is not required at all for the determination of one’s own existence in time, their existence is really a gratuitous assumption of which no proof can ever be given.

If, on the contrary, we proceed analytically, taking the proposition, I think, which involves existence (according to the category of modality) as given, and analyse it, in order to find our whether, and how, the Ego determines its existence in space and time by it alone, the propositions of rational psychology would not start from the concept of a thinking being, in general, but from a reality, and the inference would consist in determining from the manner in which that reality is thought, after everything that is empirical in it has been removed, what belongs to a thinking being in general. This may be shown by the following Table.

As it has not been determined in the second proposition, whether I can exist and be conceived to exist as a subject only, and not also as a predicate of something else, the concept of subject is here taken as logical only, and it remains undetermined whether we are to understand by it a substance or not. In the third proposition, however, the absolute unity of apperception, the simple I, being the representation to which all connection or separation (which constitute thought) relate, assumes its own importance, although nothing is determined as yet with regard to the nature of the subject, or its subsistence. The apperception is something real, and it is only possible, if it is simple. In space, however, there is nothing real that is simple, for points (the only simple in space) are limits only, and not themselves something which, as a part, serves to constitute space. From this follows the impossibility of explaining the nature of myself, as merely a thinking subject, from the materialistic point of view. As, however, in the first proposition, my existence is taken for granted, for it is not said in it that every thinking being exists (this would predicate too much, namely, absolute necessity of them), but only, I exist, as thinking, the proposition itself is empirical, and contains only the determinability of my existence, in reference to my representations in time. But as for that purpose again I require, first of all, something permanent, such as is not given to me at all in internal intuition, so far as I think myself, it is really impossible by that simple self-consciousness to determine the manner in which I exist, whether as a substance or as an accident. Thus, if materialism was inadequate to explain my existence, spiritualism is equally insufficient for that purpose, and the conclusion is, that, in no way whatsoever can we know anything of the nature of our soul, so far as the possibility of its separate existence is concerned.

And how indeed should it be possible by means of that unity of consciousness which we only know because it is indispensable to us for the very possibility of experience, to get beyond experience (our existence in life), and even to extend our knowledge to the nature of all thinking beings in general, by the empirical, but, with reference to every kind of intuition, undetermined proposition, I think.

There is, therefore, no rational psychology, as a doctrine, furnishing any addition to our self-knowledge, but only as a discipline, fixing unpassable limits to speculative reason in this field, partly to keep us from throwing ourselves into the arms of a soulless materialism, partly to warn us against losing ourselves in a vague, and, with regard to practical life, baseless spiritualism. It reminds us at the same time to look upon this refusal of our reason to give a satisfactory answer to such curious questions, which reach beyond the limits of this life, as a hint to turn our self-knowledge away from fruitless speculations to a fruitful practical use — a use which, though directed always to objects of experience only, derives its principle from a higher source, and so regulates our conduct, as if our destination reached far beyond experience, and therefore far beyond this life.

We see from all this, that rational psychology owes its origin to a mere misunderstanding. The unity of consciousness, on which the categories are founded, is mistaken for an intuition of the subject as object, and the category of substance applied to it. But that unity is only the unity in thought, by which alone no object is given, and to which, therefore, the category of substance, which always presupposes a given intuition, cannot be applied, and therefore the subject cannot be known. The subject of the categories, therefore, cannot, by thinking them, receive a concept of itself, as an object of the categories; for in order to think the categories, it must presuppose its pure self-consciousness, the very thing that had to be explained. In like manner the subject, in which the representation of time has its original source, cannot determine by it its own existence in time; and if the latter is impossible, the former, as a determination of oneself (as of a thinking being in general) by means of the categories, is equally so.1

*     *     *     *     *     *     *     *

Thus vanishes, as an idle dream, that knowledge which was to go beyond the limits of possible experience, and was connected no doubt with the highest interests of humanity, so far at least as speculative philosophy was to supply it. Yet no unimportant service has thus been rendered to reason by the severity of our criticism, in proving, at the same time, the impossibility of settling anything dogmatically with reference to an object of experience, beyond the limits of experience, and thus securing it against all possible assertions to the contrary. This can only be done in two ways, either by proving one’s own proposition apodictically, or, if that does not succeed, by trying to discover the causes of that failure, which, if they lie in the necessary limits of our reason, must force every opponent to submit to exactly the same law of renunciation with reference to any claims to dogmatic assertion.

Nothing is lost, however, by this with regard to the right, nay, the necessity of admitting a future life, according to the principles of practical, as connected with the speculative employment of reason. It is known besides, that a purely speculative proof has never been able to exercise any influence on the ordinary reason of men. It stands so entirely upon the point of a hair, that even the schools can only keep it from falling so long as they keep it constantly spinning round like a top, so that, even in their own eyes, it yields no permanent foundation upon which anything could be built. The proofs which are useful for the world at large retain their value undiminished, nay, they gain in clearness and natural power, by the surrender of those dogmatical pretensions, placing reason in its own peculiar domain, namely, the system of ends, which is, however, at the same time the system of nature; so that reason, as a practical faculty by itself, without being limited by the conditions of nature, becomes justified in extending the system of ends, and with it, our own existence, beyond the limits of experience and of life. According to the analogy with the nature of living beings in this world, in which reason must necessarily admit the principle that no organ, no faculty, no impulse, can be found, as being either superfluous or disproportionate to its use, and therefore purposeless, but that everything is adequate to its destination in life, man, who alone can contain in himself the highest end of all this, would be the only creature excepted from it. For, his natural dispositions, not only so far as he uses them according to his talents and impulses, but more especially the moral law within him, go so far beyond all that is useful and advantageous in this life, that he is taught thereby, in the absence of all advantages, even of the shadowy hope of posthumous fame, to esteem the mere consciousness of righteousness beyond everything else, feeling an inner call, by his conduct in this world and a surrender of many advantages, to render himself fit to become the citizen of a better world, which exists in his idea only. This powerful and incontrovertible proof, accompanied by our constantly increasing recognition of a design pervading all that we see around us, and by a contemplation of the immensity of creation, and therefore also by the consciousness of an unlimited possibility in the extension of our knowledge, and a desire commensurate therewith, all this remains and always will remain, although we must surrender the hope of ever being able to understand, from the mere theoretical knowledge of ourselves, the necessary continuance of our existence.

Conclusion of the Solution of the Psychological Paralogism

The dialectical illusion in rational psychology arises from our confounding an idea of reason (that of a pure intelligence) with the altogether indefinite concept of a thinking being in general. What we are doing is, that we conceive ourselves for the sake of a possible experience, taking no account, as yet, of any real experience, and thence conclude that we are able to become conscious of our existence, independently of experience and of its empirical conditions. We are, therefore, confounding the possible abstraction of our own empirically determined existence with the imagined consciousness of a possible separate existence of our thinking self, and we bring ourselves to believe that we know the substantial within us as the transcendental subject, while what we have in our thoughts is only the unity of consciousness, on which, as on the mere form of knowledge, all determination is based.

The task of explaining the community of the soul with the body does not properly fall within the province of that psychology of which we are here speaking, because that psychology tries to prove the personality of the soul, apart also from that community (after death), being therefore transcendent, in the proper sense of that word, inasmuch as, though dealing with an object of experience, it deals with it only so far as it has ceased to be an object of experience. According to our doctrine, however, a sufficient answer may be returned to that question also. The difficulty of the task consists, as is well known, in the assumed heterogeneousness of the object of the internal sense (the soul), and the objects of the external senses, the formal condition of the intuition with regard to the former being time only, with regard to the latter, time and space. If we consider, however, that both kinds of objects thus differ from each other, not internally, but so far only as the one appears externally to the other, and that possibly what is at the bottom of phenomenal matter, as a thing by itself, may not be so heterogeneous after all as we imagine, that difficulty vanishes, and there remains that one difficulty only, how a community of substances is possible at all; a difficulty which it is not the business of psychology to solve, and which, as the reader will easily understand, after what has been said in the Analytic of fundamental powers and faculties, lies undoubtedly beyond the limits of all human knowledge.

General Note on the Transition from Rational Psychology to Cosmology

The proposition, I think, or, I exist thinking, is an empirical proposition. Such a proposition is based on an empirical intuition, and its object is phenomenal: so that it might seem as if, according to our theory, the soul was changed altogether, even in thinking, into something phenomenal, and our consciousness itself, as merely phenomenal, would thus indeed refer to nothing.

Thinking, taken by itself, is a logical function only, and therefore pure spontaneity, in connecting the manifold of a merely possible intuition. It does not represent the subject of consciousness, as phenomenal, for the simple reason, that it takes no account whatsoever of the manner of intuition, whether it be sensuous or intellectual. I do not thereby represent myself to myself, either as I am, or as I appear to myself, but I only conceive of myself, as of any other object, without taking account of the manner of intuition. If thereby I represent myself as the subject of my thoughts, or as the ground of thinking, these modes of representation are not the categories of substance or cause, because these are functions of thought (judgment) as applied already to our sensuous intuition, such sensuous intuition being necessary, if I wish to know myself. But I only wish to become conscious of myself as thinking, and as I take no account of what my own self may be as a phenomenon, it is quite possible that it might be a phenomenon only to me, who thinks, but not to me, so far as I am thinking. In the consciousness of myself in mere thinking I am the substance itself, but of that substance nothing is thus given me for thinking.

The proposition I think, if it means I exist thinking, is not merely logical function, but determines the subject (which then is at the same time object) with reference to its existence, and is impossible without the internal sense, the intuition of which always supplies the object, not as a thing by itself, but as phenomenal only. Here, therefore, we have no longer mere spontaneity of thinking, but also receptivity of intuition, that is, the thinking of myself applied to the empirical intuition of the same subject. In that empirical intuition the thinking self would have to look for the conditions under which its logical functions can be employed as categories of substance, cause, etc., in order not only to distinguish itself as an object by itself, through the Ego, but to determine the mode of its existence also, that is, to know itself as a noumenon. This, as we know, is impossible, because the internal empirical intuition is sensuous, and supplies us with phenomenal data only, which furnish nothing to the object of the pure consciousness for the knowledge of its own separate existence, but can serve the purpose of experience only.

Supposing, however, that we should hereafter discover, not indeed in experience, but in certain (not only logical rules, but) a priori established laws of pure reason, concerning our existence, some ground for admitting ourselves, entirely a priori, as determining and ruling our own existence, there would then be a spontaneity by which our reality would be determinable without the conditions of empirical intuition, and we should then perceive that in the consciousness of our existing there is contained a priori something which may serve to determine with respect to some inner faculty, our existence, which otherwise can be determined sensuously only with reference to an intelligible, though, of course, an ideal world only.

This, however, would not in the least benefit the attempts of rational psychology. For though through that wonderful faculty, which becomes first revealed to myself by the consciousness of a moral law, I should have a principle, purely intellectual, for a determination of my existence, what would be its determining predicates? No other but those which must be given to me in sensuous intuition; and I should therefore find myself again in the same situation where I was before in rational psychology, requiring sensuous intuitions in order to give significance to the concepts of my understanding, such as substance, cause, etc., by which alone I can gain a knowledge of myself; and these intuitions can never carry me beyond the field of experience. Nevertheless, for practical purposes, which always concern objects of experience, I should be justified in applying these concepts, in analogy with their theoretical employment, to liberty also and to the subject of liberty, by taking them only as logical functions of subject and predicate,1 of cause and effect. According to them, acts or effects, as following those (moral) laws, would be so determined that they may together with the laws of nature be explained in accordance with the categories of substance and cause; though arising in reality from a totally different principle. All this is only meant to prevent a misunderstanding to which our doctrine, which represents self-intuition as purely phenomenal, might easily be exposed. In what follows we shall have occasion to make good use of it.

SUPPLEMENT XXVIII

[See page 400]

I have sometimes called it formal idealism also, in order to distinguish it from the material or common idealism, which doubts or denies the very existence of external things. In some cases it seems advisable to use these terms rather than those in the text, in order to prevent all misunderstanding. (This is an additional note in the Second Edition.)

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[1 ]‘Whatever’ is omitted in the Second Edition.

[1 ]If one wished to use here the usual subterfuge that realitates noumena, at least, cannot oppose each other, it would be necessary to produce an example of such pure and non-sensuous reality, to enable us to see whether it was something or nothing. No example, however, can be produced, except from experience, which never offers us anything but phenomena; so that this proposition means really nothing but that a concept, which contains affirmatives only, contains no negative, a proposition which we at least have never doubted.

[1 ]The interest which the human mind takes in morality (an interest which, as I believe, is necessary to every rational being) is natural, though it is not undivided, and always practically preponderant. If you strengthen and increase that interest, you will find reason very docile, and even more enlightened, so as to be able to join the speculative with the practical interests. If you do not take care that you first make men at least moderately good, you will never make them honest believers.

[1 ]Cosmical concept is meant here for a concept relating to what must be of interest to everybody: while I determine the character of a science, according to scholastic concepts, if I look upon it only as one of many crafts intended for certain objects.

[1 ]It must not be supposed that I mean by this what is commonly called physica generalis, and which is rather mathematics, than a philosophy of nature. For the metaphysic of nature is entirely separate from mathematics, and does not enlarge our knowledge as much as mathematics; but it is, nevertheless, very important, as supplying a criticism of the pure knowledge of the understanding that should be applied to nature. For want of its guidance, even mathematicians, given to certain common concepts which in reality are metaphysical, have unconsciously encumbered physical science with hypotheses which vanish under a criticism of those principles, without however causing the least detriment to the necessary employment of mathematics in this field.

[1 ]Kant himself in a letter to Schütz (Darstellung seines Lebens von seinem Sohn, Halle, 1835. Band. II. S. 208) pointed out the mistake which appears in the preface to the 2nd edition, namely, gleichseitig (equilateral), instead of gleichschenkelig (isosceles).

[1 ]I am not closely following here the course of the history of the experimental method, nor are the first beginnings of it very well known.

[1 ]This method, borrowed from the student of nature, consists in our looking for the elements of pure reason in that which can be confirmed or refuted by experiment. Now it is impossible, in order to test the propositions of pure reason, particularly if they venture beyond all the limits of possible experience, to make any experiment with their objects (as in natural science); we can therefore only try with concepts and propositions which we admit a priori, by so contriving that the same objects may be considered on one side as objects of the senses and of the understanding in experience, and, on the other, as objects which are only thought, intended, it may be, for the isolated reason which strives to go beyond all the limits of experience. This gives us two different sides to be looked at; and if we find that, by looking on things from that twofold point of view, there is an agreement with the principle of pure reason, while by admitting one point of view only, there arises an inevitable conflict with reason, then the experiment decides in favour of the correctness of that distinction.

[1 ]This experiment of pure reason has a great similarity with that of the chemists, which they sometimes call the experiment of reduction, or the synthetical process in general. The analysis of the metaphysician divided pure knowledge a priori into two very heterogeneous elements, namely, the knowledge of things as phenomena and of things by themselves. Dialectic combines these two again, to bring them into harmony with the necessary idea of the unconditioned, demanded by reason, and then finds that this harmony can never be obtained, except through the above distinction, which therefore must be supposed to be true.

[1 ]In the same manner the laws of gravity, determining the movements of the heavenly bodies, imparted the character of established certainty to what Copernicus had assumed at first as an hypothesis only, and proved at the same time the invisible force (the Newtonian attraction) which holds the universe together, which would have remained for ever undiscovered, if Copernicus had not dared, by an hypothesis, which, though contradicting the senses, was yet true, to seek the observed movements, not in the heavenly bodies, but in the spectator. I also propose in this preface my own view of metaphysics, which has so many analogies with the Copernican hypothesis, as an hypothesis only, though, in the Critique itself, it is proved by means of our representations of space and time, and the elementary concepts of the understanding, not hypothetically, but apodictically; for I wish that people should observe the first attempts at such a change, which must always be hypothetical.

[1 ]In order to know an object, I must be able to prove its possibility, either from its reality, as attested by experience, or a priori by means of reason. But I can think whatever I please, provided only I do not contradict myself, that is, provided my conception is a possible thought, though I may be unable to answer for the existence of a corresponding object in the sum total of all possibilities. Before I can attribute to such a concept objective reality (real possibility, as distinguished from the former, which is purely logical), something more is required. This something more, however, need not be sought for in the sources of theoretical knowledge, for it may be found in those of practical knowledge also.

[1 ]The only thing which might be called an addition, though in the method of proof only, is the new refutation of psychological idealism, and the strict (and as I believe the only possible) proof of the objective reality of external phenomena on p. 275 (Suppl. XXI). That idealism may be considered entirely innocent with respect to the essential aims of metaphysic (though it is not so in reality), yet it remains a scandal to philosophy, and to human reason in general, that we should have to accept the existence of things without us (from which we derive the whole material of knowledge for our own internal sense) on faith only, unable to meet with any satisfactory proof an opponent, who is pleased to doubt it. (See p. 476.) It will probably be urged against this proof that, after all, I am immediately conscious of that only which is within me, that is, of my representation of external things, and that consequently it must still remain uncertain whether there be outside me anything corresponding to it or not. But by internal experience I am conscious of my existence in [p. xl] time (consequently also, of its determinability in time); and this is more than to be conscious of my representation only, and yet identical with the empirical consciousness of my existence, which can be itself determined only by something connected with my existence, yet outside me. This consciousness of my existence in time is therefore connected as identical with the consciousness of relation to something outside me; so that it is experience, and not fiction, sense, and not imagination, which indissolubly connects the external with my internal sense. The external sense is by itself a relation of intuition to something real outside me; and its real, in contradistinction to a purely imaginary character, rests entirely on its being indissolubly connected with internal experience, as being the condition of its possibility. This is what happens here. If with the intellectual consciousness of my existence in the representation, I am, which accompanies all my judgments and all acts of my understanding, I could at the same time connect a determination of that existence of mine by means of intellectual intuition, then that determination would not require the consciousness of relation to something outside me. But although that intellectual consciousness comes first, the inner intuition, in which alone any existence can be determined, is sensuous and dependent on the condition of time; and that determination again, and therefore internal experience itself, depends on something permanent which is not within me, consequently on something outside me only, to which I must consider myself as standing in a certain relation. Hence the reality of the external sense is necessarily connected, in order to make experience possible at all, with the reality of the internal sense; that is, I am conscious, with the same certainty, that there are things outside me which have a reference to my sense, as that I exist myself in time. In order to ascertain to what given intuitions objects outside me really correspond (these intuitions belonging to the external sense, and not to the faculty of imagination), we must in each single case apply the rules according to which experience in general (even internal) is distinguished from imaginations, the proposition that there really is an external experience being always taken for granted. It may be well to add here the remark that the representation of something permanent in existence is not the same as a permanent representation; for this (the representation of something permanent in existence) can change and alternate, as all our representations, even those of matter, and may yet refer to something permanent, which must therefore be something external, and different from all my representations, the existence of which is necessarily involved in the determination of my own existence, and constitutes with it but one experience, which could never take place internally, unless (in part) it were external also. The how admits here of as little explanation as the permanent in time in general, the co-existence of which with the variable produces the concept of change.

[1 ]According to an emendation adopted both by Vaihinger and Adickes.

[1 ]This paragraph from It is true to intuition seems to have been a marginal note, as shown by Dr. Vaihinger. See Translator’s Preface, p. lii.

[1 ]One might doubt this with regard to pure natural science; but one has only to consider the different propositions which stand at the beginning of real (empirical) physical science, those, for example, relating to the permanence of the same quantity of matter to the vis inertiae, the equality of action and reaction, etc., in order to become convinced that they constitute a physica pura, or rationalis, which well deserves to stand by itself as an independent science, in its whole extent, whether narrow or wide.

[1 ]Phenomenal predicates can be attributed to the object in its relation to our sense: as for instance to the rose its red colour, and its scent. But what is merely illusion can never be attributed to an object as a predicate, for the simple reason that the illusion attributes to the object by itself something which belongs to it only in its relation to the senses, or to a subject in general: as for instance the two handles, which were formerly attributed to Saturn. That which is never to be found in the object itself, but always in its relation to a subject, and is inseparable from its representation by a subject, is phenomenal, and the predicates of space and time are therefore rightly attributed to objects of the senses, as such. In this there is no illusion. If, on the contrary, I were to attribute to the rose by itself redness, handles to Saturn, and extension to all external objects, without restricting my judgment to the relation of these objects to a subject, we should have illusion.

[1 ]Metaphysical Elements of Natural Science.

[1 ]Whether the representations themselves are identical, and whether therefore one can be thought analytically by the other, is a matter of no consequence here. The consciousness of the one has always to be distinguished from the consciousness of the other, so far as the manifold is concerned; and everything here depends on the synthesis only of this (possible) consciousness.

[1 ]This analytical unity of consciousness belongs to all general concepts, as such. If, for instance, I think red in general, I represent to myself a property, which (as a characteristic mark) may be found in something, or can be connected with other representations; that is to say, only under a presupposed possible synthetical unity can I represent to myself the analytical. A representation which is to be thought as common to different representations, is looked upon as belonging to such as possess, besides it, something different. It must therefore have been thought in synthetical unity with other (though only possible) representations, before I can think in it that analytical unity of consciousness which makes it a conceptus communis. The synthetical unity of apperception is, therefore, the highest point with which all employment of the understanding, and even the whole of logic, and afterwards the whole of transcendental philosophy, must be connected; ay, that faculty is the understanding itself.

[1 ]Space and time, and all portions thereof, are intuitions, and consequently single representations with the manifold of their content. (See the transcendental Æsthetic.) They are not, therefore, mere concepts, through which the same consciousness, as existing in many representations, but intuitions through which many representations are brought to us, as contained in one and in its consciousness; this latter, therefore, is compounded, and these intuitions represent the unity of consciousness as synthetical, but yet as primitive. This character of singleness in them is practically of great importance (see § 25).

[1 ]The lengthy doctrine of the four syllogistic figures concerns categorical syllogisms only, and though it is really nothing but a trick for obtaining the appearance of more modes of concluding than that of the first figure, by secretly introducing immediate conclusions (consequentiae immediatae) among the premisses of a pure syllogism, this would hardly have secured its great success, had not its authors succeeded, at the same time, in establishing the exclusive authority of categorical judgments, as those to which all others must be referred. This as we showed in § 9, p. 62, is wrong.

[1 ]The proof of this rests on the represented unity of intuition, by which an object is given, and which always includes a synthesis of the manifold which is given for an intuition, and contains the relation of the latter to the unity of apperception.

[1 ]Motion of an object in space does not belong to a pure science, consequently not to geometry, because the fact that a thing is moveable cannot be known a priori, but from experience only. Motion, however, considered as describing a space, is a pure act of successive synthesis of the manifold in external intuition in general by means of productive imagination, and belongs therefore, by right, not only to geometry, but even to transcendental philosophy.

[1 ]I do not see how so much difficulty should be found in admitting that the internal sense is affected by ourselves. Every act of attention gives us an instance of it. In such an act the understanding always determines the internal sense, according to the connection which it thinks, to such an internal intuition as corresponds to the manifold in the synthesis of the understanding. How much the mind is commonly affected thereby anybody will be able to perceive in himself.

[2 ]The I think expresses the act of determining my own existence. What is thus given is the existence, but what is not yet given, is the manner in which I am to determine it, that is, in which I am to place within me the manifold belonging to it. For that purpose self-intuition is required, which depends on an a priori form, that is, on time, which is sensuous, and belongs to our receptivity of what is given to us as determinable. If, then, I have not another self-intuition which, likewise before the act of determination, gives the determining within me, of the spontaneity of which I am conscious only, as time gives the determinable, I cannot determine my existence as that of a spontaneously acting being, but I only represent to myself the spontaneity of my thinking, that is, of the act of determination, my existence remaining sensuous only, that is, determinable, as the existence of a phenomenon. It is, however, on account of this spontaneity that I call myself an intelligence.

[1 ]Space, represented as an object (as required in geometry), contains more than the mere form of intuition, namely, the comprehension of the manifold, which is given according to the form of sensibility, into a perceptible (intuitable) representation, so that the form of intuition gives the manifold only, while the formal intuition gives unity of representation. In the Æsthetic I had simply ascribed this unity to sensibility, in order to show that it precedes all concepts, though it presupposes a synthesis not belonging to the senses, and by which all concepts of space and time become first possible. For as by that synthesis (the understanding determining the sensibility) space and time are first given as intuitions, the unity of that intuition a priori belongs to space and time, and not to the concept of the understanding. (See § 24.)

[1 ]In this manner it is proved that the synthesis of apprehension, which is empirical, must necessarily conform to the synthesis of apperception, which is intellectual, and contained in the category entirely a priori. It is one and the same spontaneity, which there, under the name of imagination, and here, under the name of understanding, brings connection into the manifold of intuition.

[1 ]Lest anybody should be unnecessarily frightened by the dangerous consequences of this proposition, I shall only remark that the categories are not limited for the purpose of thought by the conditions of our sensuous intuition, but have really an unlimited field. It is only the knowledge of that which we think, the determining of an object, that requires intuition, and even in the absence of intuition, the thought of the object may still have its true and useful consequences, so far as the subjective use of reason is concerned. That use of reason, however, as it is not always directed to the determination of the object, that is, to knowledge, but also to the determination of the subject, and its volition, cannot be treated of in this place.

[1 ]Kant does not carry the division into paragraphs in his second edition further, because, as he says, he has to treat no more of elementary concepts, and prefers, in representing their employment, to adopt a continuous treatment, without paragraphs.

[1 ]This passage has been translated as amended by Kant himself in the Preface to the Second Edition (p. 386).

[1 ]The immediate consciousness of the existence of external things is not simply assumed in the preceding theorem, but proved, whether we can understand the possibility of this consciousness or not. The question with regard to that possibility would come to this, whether we have an internal sense only, and no external sense, but merely an external imagination. It is clear, however, that, even in order to imagine only something as external, that is, to represent it to the senses in intuition, we must have an external sense, and thus distinguish immediately the mere receptivity of an external intuition from that spontaneity which characterizes every act of imagination. For merely to imagine an external sense would really be to destroy the faculty of intuition, which is to be determined by the faculty of imagination.

[1 ]Read der instead of als.

[1 ]It is easy enough to conceive the non-existence of matter, but the ancients did not infer from this its contingency. Not even the change of being and not-being of any given state of a thing, which constitutes all change, can prove the contingency of that state, as if from the reality of its opposite. The rest of a body, for instance, following on its motion, does not yet prove the contingency of that motion, because the former is the opposite of the latter. The opposite here is opposed to the other, not realiter, but logically only. In order to prove the contingency of the motion of a body, we should have to prove that instead of the motion at the antecedent point of time, it would have been possible for the body to have been at rest at that very time, not that it is at rest afterwards; for in this case both opposites are quite consistent with each other.

[1 ]The thinking is taken in each of the two premisses in a totally different meaning: — in the major, as it refers to an object in general (and therefore also as it may be given in intuition), but in the minor, only as it exists in its relation to self-consciousness, where no object is thought of, but where we only represent the relation to the self as the subject (as the form of thought). In the former, things are spoken of that cannot be conceived otherwise than as subjects; while in the second we do not speak of things, but of the thinking (abstraction being made of all objects), wherein the Ego always serves as the subject of consciousness. The conclusion, therefore, ought not to be that I cannot exist otherwise than as a subject, but only, that in thinking my existence I can use myself as the subject of a judgment only. This is an identical proposition, and teaches us nothing whatever as to the mode of our existence.

[1 ]Clearness is not, as the logicians maintain, the consciousness of a representation; for a certain degree of consciousness, though insufficient for recollection, must exist, even in many dark representations, because without all consciousness we should make no distinction in the connection of dark representations, which yet we are able to do with the notae of many concepts (such as those of right and justice, or as the musician does who in improvising strikes several keys at once). A representation is clear in which the consciousness is sufficient for a consciousness of its difference from others. If the consciousness is sufficient for distinguishing, but not for a consciousness of the difference, the representation would still have to be called dark. There is, therefore, an infinite number of degrees of consciousness, down to its complete vanishing.

[1 ]Those who, in establishing the possibility of a new theory, imagine that they have done enough if they can show triumphantly that no one can show a contradiction in their premisses (as do those who believe that they understand the possibility of thinking, of which they have an example in the empirical intuitions of human life only, even after the cessation of life) can be greatly embarrassed by other possible theories, which are not a whit bolder than their own. Such is, for instance, the possibility of a division of simple substance into several, or of the coalition of several substances into one simple substance. For although divisibility presupposes a composite, it does not necessarily require a composite of substances, but of degrees only (of the manifold faculties) of one and the same substance. As, then, we may conceive all powers and faculties of the soul, even that of consciousness, as diminished by one-half, the substance still remaining, we may also represent to ourselves, without any contradiction, that extinguished half as preserved, though not within it, but outside it, so that as the whole of what is real in it and has a degree, and therefore the whole existence of it, without any rest, has been halved, another separate substance would arise apart from it. For the plurality, which has been divided, existed before, though not as a plurality of substances, yet of every reality as a quantum of existence in it, and the unity of substance was only a mode of existence, which by mere division has been changed into a plurality of substantiality. In the same manner several simple substances might coalesce again into one, nothing being lost thereby, but merely the plurality of substantiality; so that one substance would contain in itself the degree of reality of all former substances together. We might suppose that the simple substances which give us matter as a phenomenon (not indeed through a mechanical or chemical influence upon each other, but yet, it may be, by some unknown influence, of which the former is only a manifestation), produce by such a dynamical division of parental souls, taken as intensive quantities, what may be called child-souls, while they themselves repair their loss again through a coalition with new matter of the same kind. I am far from allowing the slightest value of validity to such vague speculations, and I hope that the principles of our Analytic have given a sufficient warning against using the categories (as, for instance, that of substance) for any but empirical purposes. But if the rationalist is bold enough to create an independent being out of the mere faculty of thought, without any permanent intuition, by which an object can be given, simply because the unity of apperception in thought does not allow him to explain it as something composite, instead of simply confessing that he cannot explain the possibility of a thinking nature, why should not a materialist, though he can as little appeal to experience in support of his theories, be entitled to use the same boldness, and use his principle for the opposite purpose, though retaining the formal unity on which his opponent relied?

[1 ]The ‘I think’ is, as has been stated, an empirical proposition, and contains within itself the proposition, I exist. I cannot say, however, everything which thinks exists; for in that case the property of thinking would make all beings which possess it necessary beings. Therefore, my existence cannot, as Descartes supposed, be considered as derived from the proposition, I think (for in that case the major, everything that thinks exists, ought to have preceded), but is identical with it. It expresses an indefinite empirical intuition, that is, a perception (and proves, therefore, that this proposition, asserting existence, is itself based on sensation, which belongs to sensibility), but it precedes experience, which is meant to determine the object of perception through the categories in respect to time. Existence, therefore, is here not yet a category, which never refers to an indefinitely given object, but only to one of which we have a concept, and of which we wish to know whether it exists also apart from that conception or no. An indefinite perception signifies here something real only that has been given merely for thinking in general, not therefore as a phenomenon, nor as a thing by itself (noumenon), but as something that really exists and is designated as such in the proposition, I think. For it must be observed, that if I have called the proposition, I think, an empirical proposition, I did not mean to say thereby, that the ego in that proposition is an empirical representation; it is rather purely intellectual, because it belongs to thought in general. Without some empirical representation, however, which supplies the matter for thought, the act, I think, would not take place, and the empirical is only the condition of the application or of the use of the pure intellectual faculty.

[1 ]It is necessary to put a comma after Prädicats.