174 INTRODUCTION 



trary or at least mind-made presuppositions \ Finally in 

 the Critique of Pure Reason we have Kant's solution of the 

 problem as to the relations between a priori and a posteriori, 

 thought and experience. And his contention is that the 

 a priori is not merely that which is self-evident and can 

 be expressed in an analytic judgment, but that which 

 experience universally and necessarily involves as the 

 condition of its possibility. 



This, after all, is but the working out of what is out- 

 lined by Leibniz, when he insists on l compossibility, ' or 

 necessity arising from the system of things, as the ground 

 of reality. For Leibniz the real is the 'fitting,' that 

 which has its place in the best possible system or world : 

 for Kant the real is that which is in an orderly experience 

 constituted by principles which are the logical a priori 

 conditions of its possibility. In the philosophy of Kant, 

 accordingly, we have a more thorough application of the 

 principle of sufficient reason, which Leibniz had imper- 

 fectly applied. Leibniz's explanation of the existence of 

 the actual system of things as the result of a choice among 

 all possible worlds is due to the inconsistency in his posi- 

 tion which comes from working with two co-ordinate first 

 principles. The totality of possible worlds is at once a 

 system and not a system. If it were a system, the choice 

 by God of the best possible world would be determined 

 by the nature of the whole system of possibles. The best 

 possible world would be the best world in that system, 

 and thus the problem of Leibniz would not be solved by 

 the * choice/ but would merely be carried a stage farther 

 back. On the other hand, if the totality of possible 

 worlds were not a system, the choice of God would prac- 

 tically be arbitrary : at least it would be grounded on no 



1 Of. Untersuchung uber die Deutlichkeit der Grundsdtze der naturlichen 

 Thcologie und der Moral (1764^ (Rosenkranz, i. 75 ; Hartenstein, i. 63). 

 See also Kant's Inaugural Thesis on becoming Professor in Konigs- 

 berg, De mundi sensililis atque intelligibilis forma et principiis (1770), in 

 which the distinction between sense and understanding is brought 

 to the sharpest point. (Rosenkranz, i. 301 ; Hartenstein, iii. 123.) 



