106 INTRODUCTION 



while, on the other hand, the Monad whose perceptions 

 are clearer and more distinct is said to be so far active in 

 relation to the other or (ideally, of course) to act upon 

 it \ Thus, as we have already seen, the pre-established 

 harmony is the basis of the inter-relation of the Monads 

 and of their mutual changes 2 . Further, as clear and 

 distinct perceptions are simply the unfolding (explication) 

 or explanation of the corresponding more confused per- 

 ceptions, the action of one substance upon another is to 

 be regarded as meaning that the active substance, in so 

 far as it is active, contains within itself (or, simply, is) the 

 explanation of the passive substance, in so far as it is 

 passive. Substances acting upon others are, accordingly, 

 those in which the reason of the changes in the others 

 may be read more distinctly than in those in which the 

 changes actually occur 3 . Thus the connexion between 

 cause and effect in different substances is a purely ideal 

 relation, a harmony of internal changes and operations, 

 implying no physical influence of one substance upon 

 another. And, further, the cause of any change is not its 

 obscure antecedent nor any power or activity prior in 



1 Cf. Spinoza's views of action and passion hi Ethics, Part iii, 

 especially Defs. i and 2, and Props, i, 2, and 3. Also Ethics, 

 Part v. Prop. 40, Corollary. 



a Cf. p. 40 ; see also Lettre a Arnauld (1690) (G-. ii. 135 ; E. 107 b), in 

 which Leibniz gives a summary of his position : ' There must be 

 everywhere in body substances indivisible, unborn and imperish- 

 able, having something corresponding to souls. . . . Each of these 

 substances contains in its own nature " legem continuationis seriei 

 suarum operationum " [the principle of succession of the series of its 

 own operations] and all that has happened and shall happen to 

 .it. All its actions come from its own inner being [fonds], except 

 Its dependence upon God. Each substance expresses the entire 

 universe, but one does so more distinctly than another, and each 

 expresses it more especially with regard to certain things and 

 according to its own point of view. The_union of soul with body, 

 and indeed the operation of one substance upon another, consists 

 only in the perfect mutual accord of substances, definitely estab- 

 lished through the order of their first creation, in virtue of which 

 each substance, following its own laws, agrees with the rest, 

 meeting their demands ; and the operations of the one thus follow 

 or accompany the operations or change of the other.' 



3 Cf. Monadology, 49 sqq. 



