A Treatise of Human Nature / Being an Attempt to Introduce the Experimental Method Into Moral Subjects; and Dialogues Concerning Natural Religion

by David Hume

How do I know my own real existence?—Locke’s answer.

143. We have finally to notice the way in which Locke maintains our knowledge of the ‘real existence’ of thinking substance, both as that which ‘we call our mind,’ and as God. Of the former first. ‘Experience convinces us that we have an intuitive knowledge of our own existence…. If I know I feel pain, it is evident I have as certain perception of my own existence as of the pain I feel. If I know I doubt, I have as certain perception of the existence of the thing doubting as of that thought which I call doubt’ (Book IV. chap. ix. sec. 3). Upon this the remark must occur that the existence of a painful feeling is one thing; the existence of a permanent subject, remaining the same with itself, when the feeling is over, and through the succession of other feelings, quite another. The latter is what is meant by my own existence, of which undoubtedly there is a ‘certain perception,’ if the feeling of pain has become the ‘knowledge that I feel pain,’ and if by the ‘I’ is understood such a permanent subject. That the feeling, as ‘simple idea,’ is taken to begin with by Locke for the knowledge that I feel something, we have sufficiently seen. [1] Just as, in virtue of this conversion, it gives us ‘assurance’ of the real existence of the outer thing or material substance on the one side, so of the thinking substance on the other. It carries with it the certainty at once that I have a feeling, and that something makes me feel. But whereas, after the conversion of feeling into a felt thing has been throughout assumed—as indeed otherwise feeling could not be spoken of—a further question is raised, which causes much embarrassment, as to the real existence of such thing; on the contrary, the reference of the feeling to the thinking thing is taken as carrying with it the real existence of such thing. The question whether it really exists or no is only once raised, and then summarily settled by the sentence we have quoted, while the reality whether of existence or of essence on the part of the outward thing, as we have found to our cost, is the main burden of the Third and Fourth Books.

[1] See above, paragraphs 26 and following, and 59 and following.

It cannot be known consistently with Locke’s doctrine of real existence.

144. In principle, indeed, the answer to both questions, as given by Locke, is the same: for the reasons which he alleges for being assured of the ‘existence of a thing without us corresponding to the idea of sensation’ reduce themselves, as we have seen, to the reiteration of that reference of the idea to a thing, which according to him is originally involved in it, and which is but the correlative of its reference to a subject. This, however, is what he was not himself aware of. To him the outer and the inner substance were separate and independent things, for each of which the question of real existence had to be separately settled. To us, according to the view already indicated, it is the presence of self-consciousness, or thought as an object-to-itself, to feeling that converts it into a relation between feeling thing and felt thing, between ‘cogitative and incogitative substance.’ The source of substantiation upon each side being the same, the question as to the real existence of either substance must be the same, and equally so the answer to it. It is an answer that must be preceded by a counter question.—Does real existence mean existence independent of thought? To suppose such existence is to suppose an impossibility—one which is not the less so though the existence be supposed material, if ‘material’ means in ‘space’ and space itself is a relation constituted by the mind, ‘bringing things to and setting them by one another.’ Yet is the supposition itself but a mode of the logical substantiation we have explained, followed by an imaginary abstraction of the work of the mind from this, its own creation. Does real existence mean a possible feeling? If so, it is as clear that what converts feeling into a relation between felt thing and feeling subject cannot in this sense be real, as it is that without such conversion no distinction between real and fantastic would be possible. Does it, finally, mean individuality, in such a sense that unless I can say this or that is substance, thinking or material, substance does not really exist? If it does, the answer is that substance, being constituted by a relation by which self-conscious thought is for ever determining feelings, and which every predication represents, cannot be identified with any ‘this or that,’ though without it there could be no ‘this or that’ at all.

But he ignores this in treating of the self.

145. We have already found that Locke accepts each of the above as determinations of real existence, and that, though in spite of them he labours to maintain the real existence of outward things, he is so far faithful to them as to declare real essence unknowable. In answering the question as to ‘his own existence’ he wholly ignores them. He does not ask how the real existence of the thinking Ego sorts with his ordinary doctrine that the real is what would be in the world whether there were a mind or no; or its real identity, present throughout the particulars of experience, with his ordinary doctrine of the fictitiousness of ‘generals.’ A real existence of the mind, however, founded on the logical necessity of substantiation, rests on a shifting basis, so long as by the mind is understood a thinking thing, different in each man, to which his inner experience is referred as accidents to a substance. The same law of thought which compels such reference requires that the thinking thing in its turn, as that which is born grows and dies, be referred as an accident to some ulterior substance. ‘A fever or fall may take away my reason or memory, or both; and an apoplexy leave neither sense nor understanding, no, nor life.’ [1] Just as each outer thing turns out to be a ‘retainer to something else,’ so is it with the inner thing. Such a dependent being cannot be an ultimate substance; nor can any natural agents to which we may trace its dependence really be so either. The logical necessity of further substantiation would affect them equally, appearing in the supposition of an unknown something beyond, which makes them what they are. It is under such logical necessity that Locke, in regard to all the substances which he commonly speaks of as ultimate—God, spirit, body—from time to time gives warning of something still ulterior and unknowable, whether under the designation of substance or real essence (Book II. chap. xxiii. secs. 30 and 36). If, then, it will be said, substance is but the constantly-shifting result of a necessity of thought—so shifting that there is nothing of which we can finally say, ‘This is substance, not accident’—there can be no evidence of the ‘real existence’ of a permanent Ego in the necessary substantiation therein of my inner experience.

[1] Locke, Book III. chap. vi. sec. 4.

Sense in which the self is truly real.

146. The first result of such a consideration in a reader of Locke will naturally be an attempt to treat the inner synthesis as a fiction of thought or figure of speech, and to confine real existence to single feelings in the moments of their occurrence. This, it will seem, is to be faithful to Locke’s own clearer mind, as it frequently emerges from the still-returning cloud of scholasticism. The final result will rather be the discovery that the single feeling is nothing real, but that the synthesis of appearances, which alone for us constitutes reality, is never final or complete: that thus absolute reality, like ultimate substance, is never to be found by us—in a thinking as little as in a material thing—belonging as it does only to that divine self-consciousness, of which the presence in us is the source and bond of the ever-growing synthesis called knowledge, but which, because it is the source of that synthesis and not one of its partial results, is neither real nor knowable in the same sense as is any other object. It is this presence which alone gives meaning to ‘proofs of the being of God;’ to Locke’s among the rest. For it is in a sense true, as he held, that ‘my own real existence’ is evidence of the existence of God, since the self, in the only sense in which it is absolutely real or an ultimate subject, is already God. [1]