THE MONADOLOGY 263 



the pre-established harmony between all substances, since 

 they are all representations of one and the same uni- 

 verse 125 . (Pref. [E. 475 a ; G. vi. 39] ; Theod. 340, 352, 

 353, 358.) 



79. Souls act according to the laws of final causes 

 through appetitions, ends, and means. Bodies act 

 according to the laws of efficient causes or motions. And 

 th6 two realms, that of efficient causes and that of final 

 causes, are in harmony with one another J26 . 

 \J So. Descartes recognized that souls cannot impart any 

 force to bodies, because there is always the same quantity 



125 That is to say, the problem of the connexion between soul and 

 body is a special case of the wider problem as to the relation of 

 any one simple substance or Monad to another. 



126 They are in harmony, because ultimately the one is reducible 

 to the other. When it is said that ' souls act,' what is meant is 

 that they pass from one perception to another, i. e. that they have 

 appetition. When it is said that l bodies act/ what is meant is 

 that they change their state or their relation to other bodies, i. e. 

 that they have motion. What we call the ' state ' of a bod^v and its 

 1 relations to other bodies ' ought in strictness to be called the 

 (unconscious^ perceptions of the 



And similarly, the ' motion ' of the body is really the (unconscious) 

 appetition of its constituent Monads. Thus the difference between 

 efficient a.ind__pna.|_causes, like that between the unconscious and 

 the conscious, is merely a dmerence ot clegree. Cf. Principles of 

 Nature and of Grace , n. / From a psychological point of view, 

 Leibniz describes the parallelism of soul and body thus : 1 1 have 

 carefully examined this matter and I have shown that there are 

 really in the soul some materials of thought or objects of the 

 understanding, which the external senses do not supply, namely, 

 the soul itself and its functions (nihil est in intelleciu quod nonfuerit in 

 sensu, nisi ipse intellectus) . . . but I find nevertheless, that there is 

 never an abstract thought which is not accompanied by some 

 material images or marks [traces'], and I have made out a perfect 

 parallelism between what passes in the soul and what takes place 

 in matter, having shown that the soul, with its functions, is some- 

 thing distinct from matter but yet is always accompanied by 

 material organs, and also that the functions of the soul are always 

 accompanied by functions of its organs, which must correspond to 

 them, and that this is and always will be reciprocal.' Considerations 

 sur la Doctrine d'un Esprit Universel unique (1702) (E. 180 a ; G. vi. 

 532). 



