110 INTRODUCTION 



implied in the group, though all are really independent, 

 Its control or dominance consists solely in the distinctness 

 of its perceptions. Just as cause is not a real influence of 

 one substance upon another, but merely the relation of 

 activity in the one to corresponding passivity in the other, 

 or of distinct to confused perception, so the central 

 Monad of any compound substance has no physical con- 

 trol over the others, but is dominant because of its 

 activity and distinctness. Thus the relation between the 

 dominant Monad and the phenomena (implying other 

 Monads) which, along with it, constitute a compound 

 substance is similar to the relation between the two 

 elements, active and passive (entelechy and materia prima), 

 which together constitute simple substance or the indi- 

 vidual Monad. The dominant Monad is the entelechy or 

 soul of the compound substance, while its body is a 

 phenomenal aggregate, every portion of which in turn 

 implies a Monad or soul. But this aggregate is materia 

 secunda ; and thus we have simple substance consisting of 

 materia prima and entelechy, and compound substance 

 consisting of materia secunda and dominant Monad. 



While observing this analogy, we must not forget the 

 essential difference between simple and compound sub- 

 stance. The former alone is really substance : the latter, 

 in so far as it differs from the former, is merely sub- 

 stance by courtesy or common usage. Simple substance 

 is a concrete unity ; compound substance, in so far as it 

 is compound (i. e. apart from its soul or dominant Monad, 

 which is non-quantitative, and therefore cannot be an 

 element in a compound), is merely an aggregate. Thus 

 the materia prima or passivity of the individual Monad is 

 a name for its confused, undeveloped or implicit nature 

 taken abstractly : it is confused perception in the sub- 

 stance itself. But the materia secunda or body of the 

 compound substance is not confused perception in the 

 substance itself, for the body as compound has no 

 perception of its own, as distinct from the perceptions 



