245. If the first sentence of the above had been found by Hume in an author whom he was criticising, he would scarcely have been slow to pronounce it tautological. As it stands, it simply tells us that having seen things extended we consider their extension, and upon considering it acquire an idea of it. It is a fair sample enough of those ‘natural histories’ of the soul in vogue among us, which by the help of a varied nomenclature seem able to explain a supposed later state of consciousness as the result of a supposed earlier one, because the terms in which the earlier is described in effect assume the later. It may be said, however, that it is only by a misinterpretation of a carelessly written sentence that Hume can be represented as deriving the idea of extension from the consideration of distance; that, as the sequel shows, he regarded the ‘consideration’ and the ‘idea’ in question as equivalent, and derived from the same impression of sense. It is undoubtedly upon his account of this impression that his doctrine of extension depends. It is described as ‘an impression of coloured points disposed in a certain manner.’ To it the idea of extension is related simply as a copy; which, we have seen, properly means with Hume, as a feeling in a less lively stage is related to the same feeling in a more lively stage. It is itself, we must note, the impression of extension; and it is an impression of sense, about which, accordingly, no further question can properly be raised. Hume, indeed, allows himself to speak as if it were included in a ‘perception of visible bodies’ other than itself; just as in the passage from the fourth book previously examined, he speaks as if the perception, called extension, were a quality of some other perception. This we must regard as an exercise of the privilege which he claims of ‘speaking with the vulgar while he thought with the learned;’ since, according to him, ‘visible body,’ in any other sense than that of the impression of coloured points, is properly a name for a ‘propensity to feign’ resulting from a process posterior to all impressions of sense. The question remains whether, in speaking of an impression as one of ‘coloured points disposed in a certain manner,’ he is not introducing a ‘fiction of thought’ into the impression just as much as in calling it a ‘perception of body.’
The points must be themselves impressions, and therefore not co-existent.
246. An impression, we know, can, according to Hume, never be of an object in the sense of involving a reference to anything other than itself. When one is said, then, to be of coloured points, &c., this can only mean that itself is, or consists of, such points. Thus the question we have to answer is only a more definite form of the one previously put, Can a feeling consist of parts? In answering it we must remember that the parts, here supposed to be coloured points, must, according to Hume’s doctrine, be themselves impressions or they are nothing. Consistently with this he speaks of extension as ‘a compound impression, consisting of parts or lesser impressions, that are indivisible to the eye or feeling, and may be called impressions of atoms or corpuscles, endowed with colour and solidity.’ [1] Now, unless we suppose that a multitude of feelings of one and the same sense can be present together, these ‘lesser impressions’ must follow each other and precede the ‘compound impression.’ That is to say, none of the parts of which extension consists will be in existence at the same time, and all will have ceased to exist before extension itself comes into being. Can we, then, adopt the alternative supposition that a multitude of feelings of one and the same sense can be present together? In answering this question according to Hume’s premisses we may not help ourselves by saying that in a case of vision there really are impressions on different parts of the retina. To say that it really is so, is to say that it is so for the thinking consciousness—for a consciousness that distinguishes between what it feels and what it knows. To a man, as simply seeing and while he sees, his sight is not an impression on the retina at all, much less a combination of impressions on different parts of the retina. It is so for him only as thinking on the organs of his sight; or, if we like, as ‘seeing’ them in another, but ‘seeing’ them in a way determined by sundry suppositions (bodies, rays, and the like) which are not feelings, and therefore with Hume not possible ‘perceptions,’ at all. But it is the impression of sight, as it would be for one simply seeing and while he sees, undetermined by reference to anything other than itself, whether subject or object—an impression as it would be for a merely feeling consciousness or (in Hume’s language) ‘on the same footing with pain and pleasure’—that we have to do with when, from Hume’s point of view, we ask whether a multitude of such impressions can be present at once, i.e. as one impression.
[1] P. 345 [Book I, part II., sec. IV.]
A ‘compound impression’ excluded by Hume’s doctrine of time.
247. If this question had been brought home to Hume, he could scarcely have avoided the admission that to answer it affirmatively involved just as much of a contradiction as that which he recognises between the ‘interrupted’ and ‘continuous’ existence of objects; [1] and just as in the latter case he gets over the contradiction by taking the interrupted existence, because the datum of sense, to be the reality, and the continued existence to be a belief resulting from ‘propensities to feign,’ so in the case before us he must have taken the multiplicity of successive impressions to be the reality, and their co-existence as related parts to be a figure of speech, which he must account for as best he could. As it is, he so plays fast and loose with the meaning of ‘impression’ as to hide the contradiction which is involved in the notion of a ‘compound impression’ if impression is interpreted as feeling—the contradiction, namely, that a single feeling should he felt to be manifold—and in consequence loses the chance of being brought to that truer interpretation of the compound impression, as the thought of an object under relations, which a more honest trial of its reduction to feeling might have shown to be necessary. To convict so skilful a writer of a contradiction in terms can never be an easy task. He does not in so many words tell us that all impressions of sight must be successive, but he does tell us that ‘the impressions of touch,’ which, indifferently with those of sight, he holds to constitute the compound impression of extension, ‘change every moment upon us.’ [2] And in the immediate sequel of the passage where he has made out extension to be a compound of co-existent impressions, he derives the idea of time ‘from the succession of our perceptions of every kind, ideas as well as impressions, and impressions of reflection as well as of sensation.’ The parts of time, he goes on to say, cannot be co-existent; and, since ‘time itself is nothing but different ideas and impressions succeeding each other,’ these parts, we must conclude, are those ‘perceptions of every kind’ from which the idea of time is derived. [3] It is only, in fact, by availing himself of the distinction, which he yet expressly rejects, between the impression and its object, that he disguises the contradiction in terms of first pronouncing certain impressions, as parts of space, co-existent, and then pronouncing all impressions, as parts of time, successive. A statement that ‘as from the coexistence of visual, and also of tactual, perceptions we receive the idea of extension, so from the succession of perceptions of every kind we form the idea of time,’ would arouse the suspicion of the most casual reader; while Hume’s version of the same,—‘as ’tis from the disposition of visible and tangible objects we receive the idea of space, so from the succession of ideas and impressions we form the idea of time’ [4]—has the full ring of empirical plausibility.
[1] P. 483 and following, and p. 486 [Book I, part IV., sec. II.]
[2] P. 516 [Book I, part IV., sec. IV.].
[3] Pp. 342, 343 [Book I, part II., sec. III.].
[4] P. 342 [Book I, part II., sec. III.]