12 INTRODUCTION 



It was during the early years of his residence in 

 Hanover that Leibniz worked out the leading ideas of 

 his system. Disappointed in his hope of finding in 

 Spinoza a saviour from the errors of Descartes, and being 

 the rather confirmed, by Spinoza's conclusions, in his 

 conviction of the insufficiency of any merely mechanical 

 interpretation of things, he turned with renewed interest 

 to Plato 1 , with the result that towards 1680 he had 

 reached the conception of substance as essentially active 

 force. It is possible also that, in spite of his general 

 dissatisfaction with Spinoza's position, some of Spinoza's 

 ideas (such as that of the conatus or self-preserving 

 tendency of things) may have contributed to the develop- 

 ment of his new view of substance. One further step 

 was needed to complete the theory, namely, the recogni- 

 tion that the force constituting a substance is not a 

 universal world-principle, but something individual 

 that there are substances which are forces. To this position 

 he seems to have attained about 1684 or a little later, 

 through a return to the consideration of Aristotle and the 

 Peripatetic Schools, whose views he had set aside in his 

 boyhood, nearly twenty-five years before. The main ideas 

 of his philosophy (such as his conception of ' simple 

 substance' and his pre-established harmony) . were first 

 stated in the correspondence with Arnauld, which took 

 place between 1686 and 1690. This correspondence, 

 however, was not published as a whole until 1846 ; and 

 the learned world was first made aware that Leibniz had 

 worked out a philosophical system of his own by two 

 papers which he published in 1695 one (the Specimen 

 Dynamicum) in the Leipzig Acta Eruditontm, and the 

 other (the Systeme Nouveau) in the French Journal des 

 Savants. Leibniz uses the term 'monad' for the first 

 time in 1697. 



1 ' Of all the ancient philosophers I find Plato the most satis- 

 factory in regard to metaphysics.' Letlre a M. Bourguet (1714) (E. 

 723 a ; G. iii. 568). 



