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CHAPTER I.: A DATUM WANTED. - Herbert Spencer, The Principles of Psychology 
The Principles of Psychology (London: Longman, Brown, Green and Longmans, 1855).
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A DATUM WANTED.
§ 1. The postulates and axioms prefacing our expositions of exact science—our works on Geometry and our Mechanical Treatises—are received on the direct warrant of consciousness that they are indisputable. Similarly with all that we regard as objective truths; whether known immediately by simple intuitions, or mediately by the series of intuitions constituting a deductive argument. But when from objective truths we pass to subjective ones—when from the outer phenomena cognized, we turn to the inner phenomena presented by the act of cognition—when, after analysing knowledge, we begin to analyse that which knows, we are met by the question—What is here our test of validity? Consciousness vouches for the truth of propositions concerning external relations; but what shall vouch for the truth of propositions concerning those internal relations which constitute the phenomena of consciousness? To reply broadly that consciousness must be its own surety, involves the awkward corollary that all conclusions reached by self-analysis are true; seeing that in the individual who draws them, all such conclusions are dicta of consciousness. This corollary is manifestly inadmissible. It is clear that of such dicta, only some are true; and hence the need for a test by which these may be distinguished from the false. Unaided internal perception can no more suffice to build up a science of mind than unaided external perception can suffice to build up a science of things. As we cannot by a simple outward inspection determine with certainty the relation between two magnitudes, so we cannot by a simple inward inspection determine with certainty the relation between two states of consciousness. In the one case, as in the other, some method of verifying our empirical cognitions must be found, before any sure results can be reached. True, we cannot transcend consciousness: but we can proceed in the ascertainment of internal truths, as we proceed in the ascertainment of external ones—we can make a particular mode of perception the guarantee of all other modes. And this is obviously what we must do. Some canon of normal thinking must be found, by their congruity or incongruity with which all conclusions respecting the phenomena of consciousness may be judged. If Psychology is ever to become anything more than a mere aggregation of opinions, it can only be by the establishment of some datum universally agreed to.
Especially shall we recognize this necessity, on contemplating those logical processes, required alike for the demonstration of subjective and objective truths. What is our warrant for the various acts of thought which these involve? The validity of the conclusions we draw respecting either internal or external phenomena, depends on the validity of the successive steps through which we reach them. What is our test of this validity? That some test exists, is manifest from the fact that we reject many conclusions as worthless, from the erroneousness of the steps by which they are reached. And if there is a test, then our first care must be, having definitely identified it, to examine its nature and trustworthiness. Clearly as the chains of reasoning by which all the special conclusions of Psychology must be established, are themselves psychological operations; and as the truth of such conclusions must depend upon the right conduct of these operations; it behoves us first to inquire by what method the right conduct of these operations is to be determined. On the goodness of our criterion hinges alike our logic and all the results of our logic. Rational Psychology, therefore, must necessarily take this criterion for its starting point.
Hence the need for such General Analysis of our cognitions as shall disclose the basis of certitude common to them all. Before inquiring into the special nature of each class of cognitions, we must examine the primordial data out of which the whole of them are built. This is a needful prerequisite both for substantiating such cognitions objectively considered, and for substantiating those subjective cognitions involved in our analyses. The various external and internal intuitions which underlie the entire of our developed intelligence, and which, specifically unlike as they are, are alike in the unhesitating credence we give them, must one and all have the same guarantee. What is that guarantee?
§ 2. Even neglecting à priori considerations, the need for this preliminary inquiry is abundantly proved by the utter confusion of current opinion on all fundamental questions. The inability to come to any agreement respecting the first principles of things, affords in itself ample ground for thinking that there exists some yet unestablished datum of human knowledge, which must be found before the endless disputes can be brought to an end. That men should have constructed so many systems of thought which we hold to be irrational, yet cannot satisfactorily refute, is strong ground for suspecting that there is some law of normal thought which, though instinctively acted upon, is not entered among our logical canons. The possibility of defending theories so utterly at variance with universal belief as Idealism and Scepticism, and the doctrines of Fichte and Hegel, implies one of two things: either that there is some fundamental flaw in the modes of argument pursued, or that reason necessarily leads to unreasonable conclusions. Can there be any doubt which of these is the more probable? It is much easier to suppose that particular thinkings are incidentally fallacious, than that all thinking is essentially fallacious.
The fact that even in those who draw these incongruous inferences the intellect unceasingly protests against them, would alone be good ground for assuming that its laws have been broken. The “natural propensity,” as Hume styles it, to take a realist view of things, is one which no man ever rid himself of by proving Realism logically false. When we remember that in all other cases valid deductions eventually become beliefs—that though erroneous preconceptions may for a time shut the door on them, yet increasing knowledge by and by reverses this proceeding—when we remember this, it seems more likely that the incredible deductions of metaphysicians should be vicious than that they should form the only exceptions.
Regard the philosopher objectively. Is it not clear that the faculties he is now employing in reasoning about consciousness and ideas, are the same faculties with which in childhood he drew his simplest inferences? Must not the action of these faculties follow, throughout, the same law? Must not the results of their action be therefore congruous? And when they are not congruous, does not the fact indicate something abnormal—some nonconformity with the laws of their action—some error, as we say?
Indeed, on looking at the matter in the abstract, the logical impossibility of these theories that conflict with universal belief becomes manifest. For clearly, unless we can transcend consciousness, all metaphysics can be nothing but an analysis of our knowledge by means of our knowledge—an inquiry by our intelligence into the decisions of our intelligence. We cannot carry on such an inquiry without taking for granted the trustworthiness of our intelligence. How then can we legitimately end in proving something at variance with our primary beliefs, and so proving our intelligence fundamentally untrustworthy? Intelligence cannot prove its own invalidity because it must postulate its own validity in doing this.
There seems ample ground, then, for thinking that some logical vice underlies the incredible conclusions which metaphysicians arrive at—a vice manifestly both deep-seated and prevalent. The facts indicate a non-recognition of some primordial element in our knowledge; and further show how all-essential is the identification of it.
§ 3. But the need for a datum is most clearly seen on contemplating the efforts made to overthrow these unnatural systems. Such efforts fail from not having as a fulcrum some universally admitted truth underlying all others. Right as Reid may have been in his conviction, he cannot be said to have demonstrated that he was so. His “Inquiry into the Human Mind” contains no disproof of Scepticism, but is little more than an elaborate protest against it. Whilst now and again raising the hope that he is about to expose some fundamental error in his opponent's argument, he constantly disappoints by ending with another emphatic condemnation of the conclusion it leads to. “An absurdity too gross to merit confutation”—“palpable absurdities” which “with the adepts pass for profound discoveries”—“to reason against any of these kinds of evidence (of the senses, memory, &c.) is absurd”—such are the expressions with which he commonly winds up a paragraph; expressions that fall harmlessly on the sceptic who admits the seeming ridiculousness of his inferences, but asks how they can be untrue if logically drawn. In his later work, the “Essays on the Intellectual Powers of Man,” Reid still beats the air. He continues to assume all that Scepticism calls in question. In the chapter on “Principles taken for granted,” he says:—“I perceive figure, colour, hardness, softness, motion, resistance, and such like things. But these are qualities, and must necessarily be in something that is figured, coloured, hard or soft, that moves or resists…. We do not give the name of mind to thought, reason, or desire; but to that being which thinks, which reasons, which desires.” Thus he adopts as premisses what Hume rejects as conclusions. He finds no common ground on which he and the doubter alike stand, and standing on which they may try their strength; but having thrown down his gage, he remains outside the lists, and merely hurls at his opponent an occasional sarcasm. Regarded as contributions to Psychology, his “Essays” have merit; but as constituting an answer to Scepticism, they have none.
In the Dissertation appended to his edition of Reid's works, Sir William Hamilton places the Common-sense Philosophy on a more satisfactory footing. But though by the systematic coherence he gives to its doctrines, he makes it look more tenable, he does not render it criticism-proof. Unfortunately, some of his main positions are open to objection. Among the self-evident propositions with which he sets out, are these:—
“Consciousness is to be presumed trustworthy until proved mendacious.
The mendacity of consciousness is proved, if its data, immediately in themselves, or mediately in their necessary consequences, be shown to stand in mutual contradiction.”
Now a sceptic might very properly argue that this test is worthless. For as the steps by which consciousness is to be proved mendacious are themselves states of consciousness; and as they must be assumed trustworthy in the act of proving that consciousness is not so; the process results in assuming the trustworthiness of particular states of consciousness, to prove the mendacity of consciousness in general. Or to apply the test specifically—Let it be shown that two data of consciousness stand in contradiction. Then consciousness is mendacious. But if consciousness is mendacious, then the consciousness of this contradiction is mendacious. Then consciousness is trustworthy. And so on for ever.
If it be replied that, could it be shown, a contradiction between the data of consciousness would still be the justification of scepticism—that though it would not prove the certainty of falsehood, which implies somewhere a test of truth, it would yet prove the impossibility of determining that any judgment whatever was either true or false; the rejoinder is, that the cognition of a contradiction between two primary data of consciousness, implying as it does the union of those two data in a certain relation, is a more complex operation of consciousness than the cognition of either datum by itself; that any untrustworthiness of consciousness, did it exist, must render the compound cognition much more uncertain than the simple ones; that hence the consciousness of a contradiction can never have so great a validity as either of the primary data of consciousness between which it is supposed to exist; that thus the only logical scepticism must be directed against the seeming contradiction; and that, consequently, scepticism must destroy itself at the first step.
Doubtless all this, merely serving to show, as it does, that the mendacity of consciousness cannot be proved, and that the effort to establish, by any mental act whatever, either the validity or invalidity of consciousness, is analogous to the mechanical absurdity of trying to lift the chair one sits on, does not diminish the credibility of consciousness—merely shows that its credibility must be assumed. Sir William Hamilton's test simply fails to help us; the only harm being that the offer of a valueless guarantee lays open to cavil that which it is put forward to insure.
A much more serious objection, however, may be raised to the proposition, on which turns the whole defence of Common Sense versus Scepticism. Sir William Hamilton says:—“In the act of sensible perception I am conscious of two things;—of myself as the perceiving subject, and of an external reality in relation to my sense as the object perceived. Each of these is apprehended equally and at once in the same indivisible energy;” or, as he elsewhere phrases it—”in the same indivisible moment of intuition.“
Now this alleged simultaneity in our consciousness of subject and object, on which Sir William Hamilton relies for his proof of Realism, will not only be disputed by many as not being uniformly confirmed by their experience, but there would be no sufficient warrant for his conclusions, did experience invariably endorse his premiss. At a future stage of the argument, I propose to adduce evidence countenancing the belief, that in the act of perception our consciousness of subject and object is not simultaneous; but even were there no such evidence, this apparent simultaneity would be inadequate proof of real simultaneity.
For it must be remembered, that states of consciousness which originally occurred in distinct succession do, by constant association, come to follow one another so rapidly as to seem inseparable; and that in virtue of this law we ultimately unite a whole group of perceptions so instantaneously, that they appear as one perception. On looking at a book, we seem to take in all its leading properties “in the same indivisible energy.” We cannot detect any lapse of time between our recognition of the book as a whole and our recognition of the parts we see: yet it is universally admitted, that the unseen sides of the book are inferred from the seen sides. We cannot detect any lapse of time between our recognition of the solidity of the book and our recognition of its colour and extension: yet it is universally admitted, that the solidity is inferred from these. And as all inferred ideas must come after those from which they are inferred, it is clear that we do not recognize the various properties of the book simultaneously, though we seem to do so. Were apparent simultaneity in the acts of consciousness a proof of real simultaneity, nothing would be clearer than that we perceive an object and its distance from us “in the same indivisible moment of intuition;” for it is impossible to distinguish any interval between these perceptions. Yet no fact in Psychology is better established than this,—that the perception of a thing's distance is subsequent to the perception of the thing itself—is a deduction from the mode in which the thing affects us; and that the apparent simultaneity is in truth a succession too rapid for detection.
Hence, as there is no obvious reason why the apparent simultaneity in our consciousness of subject and object may not be of like nature, the position that subject and object are apprehended “in the same indivisible moment of intuition,” cannot be considered unquestionable; and is consequently not a fit basis for the refutation of Scepticism.
§ 4. The only further considerations of moment touching this required first principle—considerations indicating the direction in which it should be looked for—are suggested by the “Cogito ergo sum” which Descartes took for the foundation of his system. Passing over all criticisms, on the assumption that the proposition I think is more certain than the proposition I am—even granting that this last truth can become positively known only as a corollary from the first, there yet remains the fatal question—What gives validity to the therefore? Something more than the two states of consciousness, I think and I am, is involved; namely, the state of consciousness in which the relation of the one to the other is established. The absolute truth of the premiss being admitted, it is clear that before absolute truth can be claimed for the conclusion, it must be proved to be absolutely true that the one involves the other. Surely this needs verification quite as much as the proposition, I am:—nay more; seeing that the cognition of the dependence of one thing upon another is more complex, and therefore more uncertain, than the cognition of either thing by itself.
Is it not then obvious that the first thing to be investigated is that mental act whereby we recognize the validity of our convictions? The fact of choosing for a basis some such fundamental proposition as I think, in preference to the countless other possible propositions, implies that there exists a process of thought by which the relative trustworthiness of propositions is ascertained—by which we class some convictions as less questionable than others, and some as unquestionable. And similarly the fact of choosing a particular conclusion as following from the premisses rather than any other, implies a process of thought by which we distinguish a valid logical act from invalid ones. In either case, we believe one thing rather than some other thing. And the all-essential question arising alike in these cases, and in every case, is—why? Ignoring, as is requisite in a fundamental analysis, the conventional distinction between knowing and believing, and considering, as we must, our whole knowledge to be made up of beliefs, the ground-problem is, to determine the nature of a true belief. Our starting point must be, not any substantive proposition believed, but some canon of belief itself. Here only can be found the fact which underlies all other facts.
These abstract reasons for seeking the required datum in a law of correct credence, suggest a definite course of investigation. Commencing it, as seems desirable, with a somewhat different and more specific statement of the preliminary position just indicated, we shall presently find ourselves led to the desired result.