50 AMONG THE GREEKS. 



the outcome of an all-pervading movement^ which we 

 should, in nineteenth-century language, speak of 

 as an 'internal perfecting tendency.' In Aristotle's 

 conception of ' movement,' as outlined in his Phys- 

 ics, we find something very analogous to our 

 modern biological conception of transformation in 

 development, for he analyzes ' movement ' as every 

 change, as every realization of what is possible, 

 consisting in : {a) Substantial movement, origin 

 and decay, as we should now say, development and 

 degeneration ; (b) Quantitative movement, addition 

 and subtraction, or, in modern terms, the gain and 

 loss of parts ; [c) Qualitative movement, or the 

 transition of one material into another, in meta- 

 morphosis and change of function ; {d) Local move- 

 ment, or change of place, in the transposition 

 of parts. 



Thus Aristotle thought out the four essential 

 features of Evolution as a process ; but we have 

 found no evidence that he actually applied this 

 conception to the development of organisms or of 

 organs, as we do now in the light of our modern 

 knowledge of the actual stages of Evolution. This 

 enables us to understand Aristotle's view of Nature 

 as the principle of motion and rest comprised in 

 his four Causes. Here again he is more or less 

 metaphysical. The first is the 'physical Material 

 cause,' or matter itself ; the second is the ' physical 

 Formal cause,' or the forces of the ' perfecting prin- 

 ciple'; the third is the 'abstract Final cause,' the 



