and the presentation of that occurrence by the self-conscious subject to itself; and, if only he had known what he was about in the recognition, might have anticipated Kant’s distinction between the matter and form of sensation. In the Second Book, however, he will neither say explicitly that space is an impression of colour or a compound of colours--that would be to extinguish geometry; nor yet that it is impression of sense separate from that of colour--that would lay him open to the retort that he was virtually introducing a sixth sense; nor on the other hand will he boldly avow of it, as he afterwards does of body, that it is a fiction. He denies that it is a separate impression, so far as that is necessary for avoiding the challenge to specify the sense through which it is received; he distinguishes it from a mere impression of sight, when it is necessary to avoid its simple identification with colour. By speaking of it as ‘the manner in which objects exist’--so long as he is not confronted with the declarations of the Fourth Book or with the question how, the objects being impressions, their order of existence can be at once that of succession in time and of co-existence in space--he gains the credit for it of being a datum of sight, yet so far distinct from colour as to be a possible ‘foundation for an abstract idea,’ representative also of objects not coloured at all but tangible. At the same time, if pressed with the question how it could be an impression of sight and yet not interchangeable with colour, he could put off the questioner by reminding him that he never made it a ‘separate or distinct impression, but one of the manner in which objects exist.’ [1] Pp. 319, 326, 332, 335, 518. [Book I, part I., sec. IV and VII, part II, sec. I, and part IV., sec. V.] [2] P. 346. [Book I, part II., sec. IV.] [3] P. 480. [Book I, part IV., sec. II.] In his account of the idea as _abstract_, Hume really introduces distinction between feeling and conception;