48 INTRODUCTION 



the metaphysic of Leibniz, and we have seen how they 

 arise as the solution of his problem in the form which is 

 given to it by its historical setting. In the first place, 

 intension, force, or life, .in the form of perception and 

 appetition, is the essence of real, individual substance. 

 In the second place, the principle of continuity or the 

 identity of indiscernibles is the hypothesis by which 

 Leibniz endeavours to explain the system or inter-relation 

 of strictly individual substances. And, in the third place, 

 the pre-established harmony is introduced to account for 

 the possibility of change in elementary substances without 

 prejudice to the whole. 



Clear and confused Perception and Degrees of Appetition. 



We must now consider more fully the varieties of per- 

 ception and appetition which constitute the differences 

 amongst Monads. In regard to perception Leibniz adopts 

 the Cartesian distinction among ideas, with considerable 

 modifications. Descartes divided ideas into those which 

 are obscure, those which are clear, and those which are 

 distinct as well as clear. 'I call that clear,' he says, 

 ' which is present and manifest to the attentive mind, as 

 we say we see an object clearly when it is present to the 

 eye looking on, and when" it makes on the sense of sight 

 an impression sufficiently strong and definite ; but I call 

 that distinct which is clear and at the same time so 

 definitely distinguished from everything else that its 

 essence is evident to him who properly considers it 1 .' 

 And ' all the things which we clearly and distinctly con- 

 ceive are true 2 .' Leibniz follows Descartes in regarding 

 clearness and distinctness as the marks of perfection in 

 ideas or perceptions 3 ; but he does not limit the dis- 



1 Principia, i. 45. a Method, Part iv. 



3 Leibniz, however, interprets clearness and distinctness some- 

 what differently from Descartes. The distinction of one idea from 

 all others is emphasized by Descartes, while Leibniz rather lays 

 stress upon the internal distinctness of the idea, the distinctness 

 of its elements. Cf. Meditationes de Cognitione, Veritate et Ideis (1684) 



