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RECENT WORK ON THE PHILOSOPHY OF LEIBNIZ. 191 tion of his whole system, seems thus to be once for all demon- strated. It has been necessary, in the above account, to review Leibniz as well as M. Couturat, for it may almost be said that the work constitutes a new book by Leibniz. 1 For those who have not read this book, it will be impossible henceforth to speak with authority on any part of Leibniz's philosophy. Dr. Cassirer, like M. Couturat, regards Leibniz's Logic and his investigations of the principles of mathematics as the source of his metaphysical system. Nevertheless his book differs very widely from M. Couturat's in its theory as to Leibniz's opinions and as to the logical and historical order of the various parts of his philosophy. Unlike M. Couturat, the present author has not yet grasped the very modern discovery of the importance of Symbolic Logic. In the philosophy of mathematics, his views appear to agree closely with those of Prof. Hermann Cohen,' 2 to whom the book is dedicated, and to whom acknowledgments are made in the Preface. We find, accordingly, in spite of occasional references to Dedekind and Cantor, but little realisation of even the arithmetising of mathematics, and none at all of the still more recent " logicising," if such a word be permissible. Mathematics, for Dr. Cassirer, is not synonymous with Symbolic Logic, and Logic is synonymous with theory of knowledge. In both these respects, the work is Kantian, and supposes Leibniz, at least in a measure, to be also Kantian. The very rare merit of not im- puting one's own philosophy to the author one is discussing belongs to M. Couturat's work, but not, I think, to Dr. Cassirer's ; and as mathematics have of late conclusively disproved the Kantian doctrines as to their principles, the result is to rob Leibniz of his most extraordinary merit I mean, the realisation of the supreme importance of Symbolic Logic. The work, we are told in the Preface, arose out of questions as to the foundations of mathematics and mechanics. The mathe- matical motive was paramount in the formation of Leibniz's system, which is not to be judged by the rigid dogmatism of the Monadology. Kant's results e.g. as regards the ideality of space and time were largely anticipated by Leibniz : the originality of the Critical Philosophy lay rather in the form and method than in the results. Leibniz so the difference is stated in a later passage (p. 264) says that the methods of knowledge, though ideal, are valid for the real : Kant's originality lay in turning though into because in this statement. 1 M. Couturat is publishing a large collection of unpublished Leibniz MSS., which will appear shortly. 2 Cf. especially Das Princip der Infinitesimal-methode und seine Geschichte, Berlin, 1883. This work, though admirable in its historical parts, is now antiquated in its constructive theories.