132 FROM THE GREEKS TO DARWIN 



During these two progressive centuries there 

 were three classes of writers who contributed 

 more or less directly to the foundations of mod- 

 ern Evolution, before its open exposition by Buf- 

 fon: first, the Naturalists, among whom few 

 speculative questions were in vogue, who were 

 nevertheless really building up the future mate- 

 rials of thought; second, the Speculative Evo- 

 lutionists, who gave a free rein to thoroughly 

 unsound ideas upon the origin of species and re- 

 vived many of the early Greek notions ; third, the 

 great Natural Philosophers, such as da Vinci, 

 Francis Bacon, Descartes, Leibnitz, Hume, end- 

 ing with the later German school led by Kant, 

 Lessing, Herder, and Schelling. 



Influence of the Natural Philosophers 



It is a very striking fact that the basis of our 

 modern methods of studying the evolution prob- 

 lem was established not by the early naturalists 

 nor by the speculative writers, but by the nat- 

 ural philosophers, especially da Vinci, Bacon, 

 and Descartes. They alone were upon the main 

 track of modern thought. It is evident that they 

 were groping in the dark for a working theory 

 not only of the interpretation of Nature but of 

 the evolution of life, and it is remarkable that 

 they clearly perceived from the outset that the 



