354 APPENDIX I 



[superficies ambientis] 1 , and Descartes, following him, had defined 

 motion (that is, change of place) as change of neighbourhood 

 \mutatio mciniae]. Whence it seemed to follow that that which 

 is real and absolute in motion consists not in what is purely 

 'mathematical, such as change of neighbourhood or situation, 

 but in motive force [potentia matrix] itself; and if there is 

 none of this, then there is no absolute and real motion. . . . 

 Accordingly I found no other 'Ariadne thread to lead me out 

 of this labyrinth than the calculation of forces [potentiae], 

 assuming this metaphysical principle, "That the total effect 

 is always equal to its complete cause" \Quod effectus integer sit 

 semper aequalis causae suae plenae]. When I discovered that 

 this agrees perfectly with experience and satisfies all doubts, 

 I was more confirmed in my opinion that the causes of things 

 are not, so to speak, senseless [surdus] and purely mathematical, 

 like the concourse of atoms or the blind force of nature, but 

 proceed from an intelligence which employs metaphysical 

 reasons.' Phoranomus, see Arch. f. Gesch. d. Phil. i. 577. In the 

 first of these dialogues (Phoranomus, &c.) Leibniz says: 'As in 

 geometiy and numbers, through the principle of the equality 

 of the whole to all its parts, geometry is brought within the 

 ecope of an analytical calculus, so in mechanics, through the 

 principle of the equality of the eifect to all its causes or of 

 the cause to all its effects, we obtain certain equations, as it 

 were, and a kind of algebraic mechanics.' tloc. cit. p. 576. Cf. 

 Introduction to this book, Part iii. p. 107 note. 



1 Phys. A. 4. 212* 20. 



