l6o INTRODUCTION 



of the Monads as atoms his object is probably to show 

 that the Monadology expresses clearly what the atomists 

 are groping for. His leading thought in this connexion 

 is that a real whole presupposes a real unit, that is to say, 

 a unit which is essentially connected with the whole, 

 representative of it, and not in a merely accidental or 

 indeterminate relation to it. The atomists are right, he 

 would say, in insisting upon a real unit, but, on their 

 view of reality, it is impossible to find any such unit \ 



Leibniz's ' Sufficient Reason ' in relation to the ' Cause ' 

 of Descartes and Spinoza. 



When we look, not at what Leibniz was himself aware 

 of doing but at what he actually did without clearly 

 knowing it, we may regard his use of the principle of 

 sufficient reason as a development of what was implied in 

 the use which Descartes and Spinoza made of the notion 

 of ' cause.' Descartes, as we have seen 2 , develops his 

 system under the guidance of the principle of contradiction 

 alone. But in order to pass from the subjectivity of the 

 pure Ego to an objective, external reality, he finds it 

 necessary to have recourse to the principle that everything 

 must have an efficient cause which is at least as real as the 

 effect (and may be more real than it). This principle he 

 assumes without any attempt to demonstrate its validity, 

 and it is the real basis of his proofs, in the first place, of 

 the existence of God, and in the second place, of the 

 existence of an external world 3 . The proofs of the 

 existence of God form the keystone of Descartes's system. 

 Their function is to make up for the inevitable imper- 

 fections of a logic based solely on the principle of contra- 

 diction. Clinging, as he does, to the dualism of mind and 



1 Cf. this Introduction, Part ii. pp. 27 sqq. 

 3 This Introduction, Part ii. pp. 58 sqq. 



3 Cf. Meditation III and the mathematically arranged arguments 

 in the Reponses aux Deuxiemes Objections. 



