MODERN CONCEPTION OF MATTER 35 



principles ; and the most important feature of Leib- 

 nitz's philosophy was its theory of the mechanical 

 nature of physical processes — a theory that has 

 become more and more dominant in science ever 

 since. " Everything in nature," he said, " is effected 

 mechanically." Let us give one instance of his 

 mechanical theory. " Thus the organic body," he 

 writes, " of each living being is a kind of divine 

 machine, or natural automaton which infinitely sur- 

 passes all artificial automata. For a machine made 

 by the skill of man is not a machine in each of its 

 parts. For instance, the tooth of a brass wheel 

 has parts and fragments, which for us are not 

 artificial products, and which do not have the special 

 characteristics of the machine, for they give no in- 

 dication of the machine ; whereas the machines of 

 nature, namely, living bodies, are still machines in 

 their smallest parts ad infinitum. It is this that 

 constitutes the difference between nature and art, 

 that is to say, between the divine art and ours." 



A still greater apostle of the mechanic was 

 Descartes. To him matter meant merely the ex- 

 tended in space ; and from extension and motion 

 he was prepared to construct the universe. " The 

 nature," he says, " of matter or of body, considered 

 generally, does not consist in a thing being hard, or 

 heavy, or coloured, but only in its being extended 

 in length, breadth, or depth." " All variations of 



