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SUPPLEMENT XIV - Friedrich Max Müller, Critique of Pure Reason 
Immanuel Kant’s Critique of Pure Reason. In Commemoration of the Centenary of its First Publication. Translated into English by F. Max Mueller (2nd revised ed.) (New York: Macmillan, 1922).
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[See page 79]
OF THE DEDUCTION OF THE PURE CONCEPTS OF THE UNDERSTANDING
Transcendental Deduction of the Pure Concepts of the Understanding
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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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
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.
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.
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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.
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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.
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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[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.