smell, colour, hardness, softness, smoothness, and the like, as founded on the affections of the senses, do not belong to the objective body, to the thing in itself. To this he attributed only the primary qualities, i.e., such as only presuppose space and impenetrability; thus extension, figure, solidity, number, mobility. But this easily discovered Lockeian distinction was, as it were, only a youthful introduction to the distinction of Kant. The latter, starting from an incomparably higher standpoint, explains all that Locke had accepted as primary qualities, i.e., qualities of the thing in itself, as also belonging only to its phenomenal appearance in our faculty of apprehension, and this just because the conditions of this faculty, space, time, and causality, are known by us a priori. Thus Locke had abstracted from the thing in itself the share which the organs of sense have in its phenomenal appearance; Kant, however, further abstracted the share of the brain-functions (though not under that name). Thus the distinction between the phenomenon and the thing in itself now received an infinitely greater significance, and a very much deeper meaning. For this end he was obliged to take in hand the important separation of our a priori from our a posteriori knowledge, which before him had never been carried out with adequate strictness and completeness, nor with distinct consciousness. Accordingly this now became the principal subject of his profound investigations. Now here we would at once remark that Kant's philosophy has a threefold relation to that of his predecessors. First, as we have just seen, to the philosophy of Locke, confirming and extending it; secondly, to that of Hume, correcting and making use of it, a relation which is most distinctly expressed in the "Prolegomena" (that most beautiful and comprehensible of all Kant's important writings, which is far too little read, for it facilitates immensely the study of his philosophy); thirdly, a decidedly polemical and destructive relation to the Leibnitz-Wolfian philosophy. All three systems ought to be known before one proceeds
