THE CHEMICAL AND NATURAL SCIENCES 213 



tion, and intelligence. 1 Having established these 

 foundations, Aristotle explains the anatomical structure 

 and constitution of living beings, in conformity with his 

 doctrine, by final causes. This kind of explanation 

 presents difficulties which Aristotle was not always able 

 to avoid. Thus he attributed baldness to the coldness 

 of the brain, and the timidity of certain animals to the 

 size of their hearts. But as a rule teleological principles 

 led him to happy results. 



In his classification of animals, Aristotle had the 

 great merit of abandoning the dichotomous division 

 praised by Plato, which was based solely on the presence 

 or absence of some particular feature (winged and wing- 

 less, for example) . 2 According to this method of division 

 a species is composed a priori of two sub-species, which 

 in their turn are each divided into two, and so on. A 

 classification of this kind is not organic, because it 

 forcibly separates beings which are in reality closely 

 alhed, for instance, the winged ants (males and females) 

 from the wingless (workers) , the male fire-fly which has 

 wings from the female which has none. 



Aristotle also considered that, in classification, 

 anatomical characteristics should outweigh physio- 

 logical characteristics, which depend on the mode of 

 existence and on adaptation. He excelled in discover- 

 ing organic correlations and reciprocal dependences. 

 He showed how the removal of a small organ can bring 

 about a change in the whole body ; how, for example, 

 in eunuchs there is a transition from the masculine to 

 the feminine. He formulated the law of the balance of 

 organs. " Everywhere nature restores to one part what 

 she takes away from another. . . . She cannot make 

 the same expenditure in two directions. ... It is 

 impossible for her to expend the same material in 



1 E. Boutroux, Etudes d'histoire de la philosophie, Alcan, 

 Paris, 1897, p. 155. 



8 14 Gomperz, Psnseurs, III, p. 163. 



