303. Now that ‘an object exists’ can with Hume mean no more than that an ‘impression’ is felt, and without succession of feelings according to him there is no time. [1] It follows that unity in the existence of the object, being incompatible with _succession_ of feelings, is incompatible also with existence in time. Either then the unity of the object or its existence at manifold times--both being involved in the conception of identity--must be a fiction; and since ‘all impressions are perishing existences,’ perishing with a turn of the head or the eyes, it cannot be doubted which it is that is the fiction. That the existence of an object, which we call the same with itself, is broken by as many intervals of time as there are successive and different, however resembling, ‘perceptions,’ must be the fact; that it should yet be one throughout the intervals is a fiction to be accounted for, Hume accounts for it by supposing that when the separate ‘perceptions’ have a strong ‘natural relation’ to each other in the way of resemblance, the transition from one to the other is so ‘smooth and easy’ that we are apt to take it for the ‘same disposition of mind with which we consider one constant and uninterrupted perception;’ and that, as a consequence of this mistake, we make the further one of taking the successive resembling perceptions for an identical, _i.e._ uninterrupted as well as invariable object. [2] But we cannot mistake one object for another unless we have an idea of that other object. If then we ‘mistake the succession of our interrupted perceptions for an identical object,’ it follows that we have an idea of such an object--of a thing one with itself throughout the succession of impressions--an idea which can be a copy neither of any one of the impressions nor, even if successive impressions could put themselves together, of all so put together. Such an idea being according to Hume’s principles impossible, the appearance of our having it was the fiction he had to account for; and he accounts for it, as we find, by a ‘habit of mind’ which already presupposes it. His procedure here is just the same as in dealing with the idea of vacuum. In that case, as we saw, having to account for the appearance of there being the impossible idea of pure space, he does so by showing, that having ‘an idea of distance not filled with any coloured or tangible object,’ we mistake this for an idea of extension, and hence suppose that the latter may be invisible and intangible. He thus admits an idea, virtually the same with the one excluded, as the source of the ‘tendency to suppose’ which is to replace the excluded idea. So in his account of identity. Either the habit, in virtue of which we convert resembling perceptions into an identical object, is what Hume admits to be a contradiction, ‘a habit acquired by what was never present to the mind’; [3] or the idea of identity must be present to the mind in order to render the habit possible.