278. Just as that reduction of consciousness to feeling, which really excludes the idea of quantity altogether, is by Hume only recognised as incompatible with its infinite divisibility, so it is not recognised as extinguishing space altogether, but only space as a vacuum. If it be true, he says, ‘that the idea of space is nothing but the idea of visible or tangible points distributed in a certain order, it follows that we can form no idea of vacuum, or space where there is nothing visible or tangible’. [1] Here as elsewhere the acceptability of his statement lies in its being taken in a sense which according to his principles cannot properly belong to it. It is one doctrine that the ideas of space and body are essentially correlative, and quite another that the idea of space is equivalent to a feeling of sight or touch. It is of the latter doctrine that Hume’s denial of a vacuum is the corollary; but it is the former that gains acceptance for this denial in the mind of his reader. Space we have already spoken of as the relation of externality. If, abstracting this relation from the world of which it is the uniform but most elementary determination, we regard it as a relation between objects having no other determination, these become spaces and nothing but spaces—space pure and simple, vacuum. But we have known the world in confused fulness before we detach its constituent relations in the clearness of unreal abstraction. We have known bodies συγκεχυμένος [2], before we think their limits apart and out of these construct a world of pure space. It is thus in a sense true that in the development of our consciousness an idea of body precedes that of space, though the abstraction of space—the detachment of the relation so-called from the real complex of relations—precedes that of body; and it is this fact that, in the face of geometry, strengthens common sense in its position that an idea of vacuum is impossible. It is not, however, the inseparability of space from body whether in reality or for our consciousness, but its identity with a certain sort of feeling, that is implied in Hume’s exclusion of the idea of vacuum. ‘Body,’ as other than feeling, is with him as much a fiction as vacuum. That there can be no idea of vacuum, is thus in fact merely his negative way of putting that proposition of which the positive form is, that space is a compound impression of sight and touch. Having examined that proposition in the positive, we need not examine it again in the negative form. It will be more to the purpose to enquire whether the ‘tendency to suppose’ or ‘propensity to feign’ by which, in the absence of any such idea, our language about ‘pure space’ has to be accounted for, does not according to Hume’s own showing presuppose such an idea.
[1] P. 358. [Book I, part II., sec. V.]
[2] [Greek συγκεχυμένος (synkechymenos) = confused or jumbled-up. Tr.]
How it is that we talk as if we had idea of vacuum according to Hume.
279. By vacuum he understands invisible and intangible extension. If an idea of vacuum, then, is possible at all, he argues, it must be possible for darkness and mere motion to convey it. That they cannot do so alone is clear from the consideration that darkness is ‘no positive idea’ and that an ‘invariable motion,’ such as that of a ‘man supported in the air and softly conveyed along by some invisible power,’ gives no idea at all. Neither can they do so when ‘attended with visible and tangible objects.’ ‘When two bodies present themselves where there was formerly an entire darkness, the only change that is discoverable is in the appearance of these two objects: all the rest continues to be, as before, a perfect negation of light and of every coloured or tangible object’. [1] ‘Such dark and indistinguishable distance between two bodies can never produce the idea of extension,’ any more than blindness can. Neither can a like ‘imaginary distance between tangible and solid bodies.’ ‘Suppose two cases, viz. that of a man supported in the air, and moving his limbs to and fro without meeting anything tangible; and that of a man who, feeling something tangible, leaves it, and after a motion of which he is sensible perceives another tangible object. Wherein consists the difference between these two cases? No one will scruple to affirm that it consists merely in the perceiving those objects, and that the sensation which arises from the motion is in both cases the same; and as that sensation is not capable of conveying to us an idea of extension, when unaccompanied with some other perception, it can no more give us that idea, when mixed with the impressions of tangible objects, since that mixture produces no alteration upon it’. [2] But though a ‘distance not filled with any coloured or solid object’ cannot give us an idea of vacuum, it is the cause why we falsely imagine that we can form such an idea. There are ‘three relations’—natural relations according to Hume’s phraseology [3]—between it and that distance which really ‘conveys the idea of extension.’ ‘The distant objects affect the senses in the same manner, whether separated by the one distance or the other; the former species of distance is found capable of receiving the latter; and they both equally diminish the force of every quality. These relations betwixt the two kinds of distance will afford us an easy reason why the one has so often been taken for the other, and why we imagine we have an idea of extension without the idea of any object either of the sight or feeling’. [4]
[1] P. 362. [Book I, part II., sec. V.]
[2] P. 363. [Book I, part II., sec. V.]
[3] Above, § 206.
[4] P. 364. [Book I, part II., sec. V.]
His explanation implies that we have an idea virtually the same.