74 FROM THE GREEKS TO DARWIN 



idea that adaptive structures such as these teeth 

 can be produced by survivals of accidental fitness 

 and substitutes the idea of purposive progress : 



What, then, hinders but that the parts in Nature 

 may also thus arise? For instance, that the teeth 

 should arise from necessity, the front teeth sharp 

 and adapted to divide the food, the grinders broad 

 and adapted to breaking the food into pieces. 



It may be said that they were not made for this 

 purpose, but that this purposive arrangement came 

 about by chance ; and the same reasoning is applied 

 to other parts of the body in which subsistence for 

 some purpose is apparent. And it is argued that 

 where all things happened as if they were made for 

 some purpose, being aptly united by chance, these 

 were preserved, but such as were not aptly made, 

 these were lost and still perish, according to what 

 Empedocles says concerning the bull species with 

 human heads. This, therefore, and similar reasoning, 

 may lead some to doubt on this subject.-^ 



Against the fortuitous or chance hypothesis of 

 Empedocles and Democritus, Aristotle advanced 

 his own philosophy of purposive natural causa- 

 tion, which we may seek to understand by a num- 

 ber of concrete examples from his own writings. 

 Unfortunately for our purpose in these chapters, 

 his observations were far more extended in lower 

 animals and in comparative anatomy than in 

 man. 



iFor full context, see pp. 83-7. 



