142 FROM THE GREEKS TO DARWIN 



All the same, if we can imagine a few intelligible 

 and simple principles upon which the stars, and 

 earth, and all the visible world might have been pro- 

 duced (although we well know that it has not been 

 produced in this fashion), we reach a better under- 

 standing of the nature of all things than if we de- 

 scribe simply how things now are, or how we believe 

 them to have been, created. Because I believe I have 

 discovered such principles, I shall endeavour to ex- 

 plain them. 



Leibnitz (1646-1716) 



Gottfried Wilhelm Leibnitz, the first of the 

 great philosophers of Germany, advocated in his 

 writings two ideas which exerted a great but 

 partly misleading influence in biology. The first 

 was his doctrine of Continuity, and the second, 

 his doctrine of Perfectibility in the Monads. The 

 law of Perfectibility is said to have been sug- 

 gested by Bruno, but as applied to the animal 

 creation certainly came more or less directly from 

 Aristotle. It is surprising to find how Leibnitz' 

 principle of Continuity adapted itself to the idea 

 of evolution of organic beings. In part from ob- 

 servations of his own, and probably in part in- 

 fluenced by Aristotle, Leibnitz expressed as fol- 

 lows the principle of Continuity as applied to 

 life: "All natural orders of beings present but 

 a single chain, in which the different classes of 



