The arguments by which Kant seeks to show that time is not a determination of things in themselves but only a form of perception are, _mutatis mutandis_, identical with those used in his treatment of space.[1] They are, therefore, open to the same criticisms, and need no separate consideration. [1] Cf. B. 46-9, §§ 4, 5 and 6 (a), M. 28-30, §§ 5, 6 and 7 (a) with B. 38-42, § 2 (1-4), and § (3) to (a) inclusive, M. 23-6, §§ 2, 3, and 4 (a). The only qualification needed is that, since the parts of time cannot, like those of space, be said to exist simultaneously, B. § 4 (5), M. § 5, 5 is compelled to appeal to a different consideration from that adduced in the parallel passage on space (B. § 2 (4), M. § 2, 4). Since, however, B. § 4 (5), M. § 5, 5 introduces no new matter, but only appeals to the consideration already urged (B. § 4, 4, M. § 5, 4), this difference can be neglected. B. § 5, M. § 6 adds a remark about change which does not affect the main argument. Time, however, according to Kant, differs from space in one important respect. It is the form not of outer but of inner sense; in other words, while space is the form under which we perceive things, time is the form under which we perceive ourselves. It is upon this difference that attention must be concentrated. The existence of the difference at all is upon general grounds surprising. For since the arguments by which Kant establishes the character of time as a form of perception run _pari passu_ with those used in the case of space, we should expect time, like space, to be a form under which we perceive things; and, as a matter of fact, it will be found that the only _argument_ used to show that time is the form of inner, as opposed to outer, sense is not only independent of Kant's general theory of forms of sense, but is actually inconsistent with it.[2] Before, however, we attempt to decide Kant's right to distinguish between inner and outer sense, we must consider the facts which were before Kant's mind in making the distinction. [2] B. 49 (b), M. 30 (b). See pp. 109-12. These facts and, to a large extent, the frame of mind in which Kant approached them, find expression in the passage in Locke's _Essay_, which explains the distinction between 'ideas of sensation' and 'ideas of reflection'. "Whence has it [i. e. the mind] all the materials of reason and knowledge? To this I answer, in one word, from experience.... Our observation, employed either about external, sensible objects, or about the internal operations of our minds, perceived and reflected on, by ourselves, is that which supplies our understandings with all the materials of thinking. These two are the fountains of knowledge...."