Page:Leibniz Discourse on Metaphysics etc (1908).djvu/14

xiii latter carry the idea that that which suffers action, acts reciprocally and that that which acts is reacted upon."

2. Extension cannot serve to give the reason for the changes which take place in bodies, for extension with its various modifications constitutes what is called in the school terminology extrinsic characteristics, whence nothing can result for the being itself; whether a body be round or square does not affect its interior condition, nor can any particular change result for it. Furthermore every philosophy which is exclusively mechanical is obliged to deny change and to hold that everything is changeless and that there are only modifications of position or displacements in space or motion. Who does not see, however, that motion itself is a change, and should have its reason in the being which moves or which is moved, for even passive motion must correspond to something in the essence of the body moved? Besides if corporeal elements differ from one another through form, why have they one form rather than any other? Epicurus talks to us of round and hooked atoms. Why is a certain atom round and another hooked? Should not the reason be in the very substance of the atom? Therefore form, position, motion and all the extrinsic modifications of bodies should emanate from an internal principle analogous to that which Aristotle calls nature or entelechy.

3. Extension cannot be substance. On the contrary it presupposes substance. "Aside from extension there must be a subject which is extended, that is, a substance to which continuity appertains. For extension signifies only a continued repetition or multiplication of that which is expanded, a plurality, a continuity or co-existence of parts and consequently it does not suffice to explain the real nature of expanded or repeated substance whose conception precedes that of repetition."

4. Another reason given by Leibniz is that the conception of