[1] See above, paragraph 17.
As to the subject, he equivocates between singleness of feeling and individuality of conception.
221. The possibility of such a question being raised implies that the step has been already taken, which Hume ignored, from feeling to thought. His doctrine on the matter arises from that mental equivocation, of which the effects on Locke have been already noticed, [1] between the mere singleness of a feeling in time and the individuality of the object of thought as a complex of relations. If the impression is the single feeling which disappears with a turn of the head, and the idea a weaker impression, every idea must indeed be in one sense ‘individual,’ but in a sense that renders all predication impossible because it empties the idea of all content. Really, according to Hume’s doctrine of general names, it is individual in a sense which is the most remote opposite of this, as a multitude of ‘different resemblances and relations’ in ‘simplicity.’ It is just such an individual as Locke supposed to be found (so to speak) ready-made in nature, and from which he supposed the mind successively to abstract ideas less and less determinate. Such an object Hume, coming after Berkeley, could not regard in Locke’s fashion as a separate material existence outside consciousness. The idea with him is a ‘copy’ not of a thing but of an ‘impression,’ but to the impression he transfers all that individualization by qualities which Locke had ascribed to the substance found in nature; and from the impression again transfers it to the idea which ‘is but the weaker impression.’ Thus the singleness in time of the impression becomes the ‘simplicity’ of an object ‘containing many different resemblances and relations,’ and the individuality of the subject of a proposition, instead of being regarded in its true light as a temporary isolation from other relations of those for the time under view—an individuality which is perpetually shifting its limits as thought proceeds—becomes an individuality fixed once for all by what is given in the impression. Because, as is supposed, I can only ‘see’ a globe as of a certain colour and material, I can only think of it as such. If the ‘sight’ of it had been rightly interpreted as itself a complex work of thought, successively detaching felt things from the ‘flux’ of feelings and determining these by relations similarly detached, the difficulty of thinking certain of these—e.g. those designated as ‘figure’—apart from the rest would have disappeared. It would have been seen that this was merely to separate in reflective analysis what had been gradually put together in the successive synthesis of perception. But such an interpretation of the supposed datum of sense would have been to elevate thought from the position which Hume assigned to it, as a ‘decaying sense,’ to that of being itself the organizer of the world which it knows. [2]
[1] See above, paragraphs 47, 95, &c.
[2] The phrase ‘decaying sense’ belongs to Hobbes, but its meaning is adopted by Hume.
Result is a theory which admits predication, but only as singular.
222. Here, then, as elsewhere, the embarrassment of Hume’s doctrine is nothing which a better statement of it could avoid. Nay, so dexterous is his statement, that only upon a close scrutiny does the embarrassment disclose itself. To be faithful at once to his reduction of the impression to simple feeling, and to his account of the idea as a mere copy of the impression, was really impossible. If he had kept his word in regard to the impression, he must have found thought filling the void left by the disappearance, under Berkeley’s criticism, of that outward system of things which Locke had commonly taken for granted. He preferred fidelity to his account of the idea, and thus virtually restores the fiction which represents the real world as consisting of so many, materially separate, bundles of qualities—a fiction which even Locke in his better moments was beginning to outgrow—with only the difference that for the separation of ‘substances’ in space he substitutes a separation of ‘impressions’ in time. That thought (the ‘idea’) can but faintly copy feeling (the ‘impression’) he consistently maintains, but he avails himself of the actual determination of feeling by reference to an object of thought—the determination expressed by such phrases as impression of a man, impression of a globe, &c.—to charge the feeling with a content which it only derives from such determination, while yet he denies it. By this means predication can be accounted for, as it could not be if our consciousness consisted of mere feelings and their copies, but only in the form of the singular proposition; because the object of thought determined by relations, being identified with a single feeling, must be limited by the ‘this’ or ‘that’ which expresses this singleness of feeling. It is really this or that globe, this or that man, that is the subject of the proposition, according to Hume, even when in form it is general. It is true that the general name ‘globe’ or ‘man’ not merely represents a ‘particular’ globe or man, though that is all that is presented to the mind, but also ‘raises up a custom which produces any other individual idea for which we may have occasion.’ As this custom, however, is neither itself an idea nor affects the singleness of the subject idea, it does not constitute any distinction between singular and general propositions, but only between two sorts of the singular proposition according as it does, or does not, suggest an indefinite series of other singular propositions, in which the same qualities are affirmed of different individual ideas to which the subject-name has been applied.
All propositions restricted in same way as Locke’s propositions about real existence.
223. A customary sequence, then, of individual ideas upon each other is the reality, which through the delusion of words (as we must suppose) has given rise to the fiction of there being such a thing as general knowledge. We say ‘fiction,’ for with the possibility of general propositions, as the Greek philosophers once for all pointed out, stands or falls the possibility of science. Locke was so far aware of this that, upon the same principle which led him to deny the possibility of general propositions concerning real existence, he ‘suspected’ a science of nature to be impossible, and only found an exemption for moral and mathematical truth from this condemnation in its ‘bare ideality.’ Hume does away with the exemption. He applies to all propositions alike the same limitation which Locke applies to those concerning real existence. With Locke there may very well be a proposition which to the mind, as well as in form, is general—one of which the subject is an ‘abstract general idea’—but such proposition ‘concerns not existence.’ As knowledge of real existence is limited to the ‘actual present sensation,’ so a proposition about such existence is limited to what is given in such sensation. It is a real truth that this piece of gold is now being dissolved in aqua regia, when the ‘particular experiment’ is going on under our eyes, but the general proposition ‘gold is soluble’ is only an analysis of a nominal essence. With Hume the distinction between propositions that do, and those that do not, ‘concern existence’ disappears. Every proposition is on the same footing in this respect, since it must needs be a statement about an ‘idea,’ and every idea exists. ‘Every object that is presented must necessarily be existent. … Whatever we conceive, we conceive to be existent. Any idea we please to form is the idea of a being; and the idea of a being is any idea we please to form’. [1] But since, according to him, the idea cannot be separated, as Locke supposed it could, from the conditions ‘that determine it to this or that particular existence,’ propositions of the sort which Locke understood by ‘general propositions concerning substances,’ though if they were possible they would ‘concern existence’ as much as any, are simply impossible. Hume, in short, though he identifies the real and nominal essences which Locke had distinguished, yet limits the nominal essence by the same ‘particularity in space and time’ by which Locke had limited the real.
[1] p. 370 [Book I, part II., sec. VI.]