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558 world be found. At the same time he was seeking, from the other side, to deepen the conception of nature. Thus, in his De vero methodo philosophiæ et theologæ (1680), he maintains that all bodies are endowed with force, as well as extension, though he has not yet reached his conception of the individuality of substance. Professor Stein finds in Plato's view of the 'ideas ' as the only active causes of things (see the Phædo) the suggestion of this advance towards the monadology. Still, as he points out, it would be a mistake to think of Leibniz as merely borrowing from Plato, the truth being that he simply found in Plato that which helped him to answer his own problem. Similar was his relation to Aristotle, or rather to his scholastic followers, especially Aquinas. In the essay just mentioned he speaks highly of the scholastics, and later he commends the Aristotelian conception of 'entelechies' or 'substantial forms'; indeed, even when in 1686 he published, in the Discours de Métaphysique, the first draft of his own theory, it is under the name of 'substantial forms' that the doctrine of the 'monads' appears.

To appreciate the conscientious industry and the acumen displayed by Professor Stein in tracing the gradual growth of the various parts of Leibniz's philosophy until they coalesced in an organic system, his book must itself be read. The reader will there find, among other things, an interesting discussion of the origin of the term 'monad,' and a concluding chapter in which, after the birth of his own philosophy, Leibniz is seen, at least in public, as the uncompromising foe of Spinoza.

Nothing but commendation can be bestowed upon such a work as this. I believe the conclusions reached by the author, in the prosecution of his 'literary-historical' method, to be on the whole sound. But, perhaps, it may not be superfluous to point out a danger which is apt to beset that method. In such hands as Dr. Stein's, speculative insight is combined with patient investigation and judicious inference; in less skilful hands the method he sets up as a rival to the 'speculative-constructive' is apt to result in mere biographical gossip, throwing no real light upon the history of philosophy. As the late Professor Green remarked, "it is possible for knowledge about philosophers to flourish inversely as the knowledge of philosophy." And even at the best, as it seems to me, the 'historical' method can only prepare the way for a 'speculative' — which need not be a 'speculative-constructive' — method. When we have learned that Leibniz passed through a Hobbes-stage, a Cartesian-stage, a Spinoza-stage, and that in a certain year he was occupied mainly with a certain philosopher,