80 FROM THE GREEKS TO DARWIN 



say, development and degeneration; (b) quan- 

 titative 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 metamorphosis and 

 change of function; (d) local movement, or 

 change of place, in the transposition of parts. 

 Thus Aristotle thought out the four essential fea- 

 tures 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 mod- 

 ern 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 'phys- 

 ical material cause,' or matter itself; the second 

 is the 'physical formal cause,' or the forces of the 

 'perfecting principle'; the third is the 'abstract 

 final cause,' the fitness, adaptation, or purpose, 

 the good of each and all; the fourth, presiding 

 over all, is the 'efficient cause,' the prime mover, 

 or God. Aristotle attributed all the imperfec- 

 tions of Nature to the struggle between the ma- 

 terial and formal causes — ^to the resistance of 

 matter to form. There is room for difference of 

 opinion as to whether he considered the efficient 

 cause, or God, as constantly present and work- 



