GENERAL PRINCIPLES 69 



mutual isolation of simple substances is but another 

 name for their abstract self-identity. A can never become 

 B, and, as A and B are simple, no part of A can ever 

 become B, or a part of B. One Monad can never become 

 another, and no quality of one Monad can ever become 

 a quality of another. 



The principle of sufficient reason in combination with 

 the principle of contradiction yields the idea of the 

 Monad as itself the source of all the differences it con- 

 tains, the whole variety of its existence 1 . The principle 

 of contradiction requires that real substance must con- 

 tain its whole nature within itself in such a way that 

 it may be analytically deduced. The notion of substance 

 is self-explicative. Every true proposition must be ana- 

 lytic. Thus the Monad must be self-sufficient. But 

 now the principle of sufficient reason is added to explain 

 that the analysis is not necessarily completed in every 

 case, that, while substance must be self-sufficient and self- 

 explicative, its self-sufficiency is not necessarily in every 

 case fully realized. Its self-identity is not static but 

 dynamic : it is not immediately self-explaining, but pro- 

 gressively self-revealing. Many true propositions are not 

 actually but potentially analytic. While the predicate 

 of every true proposition must in some way be contained 

 in the subject, it does not follow that in each particular 

 case the relation can be made perfectly and self-evidently 

 clear 2 . The predicate must have a sufficient ground or 

 reason in the subject, but not necessarily a self-evident 

 one. The Monad must be conceived as sufficiently the 

 reason of its changes or varieties, though not self-evidently 

 the reason of each. In other words, the various per- 

 ceptions which are the variety or change in the Monad, 

 the manifold [multitude] in the simple substance, have 



1 The problem how the simple substance can contain differences is 

 the same as the problem how the principles of contradiction and 

 sufficient reason can be treated as independent and co-ordinate. 

 Of this Leibniz offers no clear solution. 



2 Cf. this Introduction, Part ii. p. 60, note 2. 



