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.