38 THE HISTORY OF BIOLOGY 



genius for the purely formal side of thinking which belongs to Aristotle 

 alone; he is in fact the founder of formal logic and in that sphere his laws 

 hold good to this day. He is, therefore, also the originator of biological 

 classification, not only because he determined those categories in which 

 human thought has since primitive times sought to arrange natural objects, 

 and because he subordinated these to the general laws of thought which he 

 created, but also in that he sought to interpret and combine into a law- 

 bound whole those phenomena which accompany life in all its forms. By 

 this work he has paved the way, as no one else has done, for the further 

 development of biology as a science based on fixed principles. And his influ- 

 ence has extended to our own day; many of the biologists of our own time 

 have revived certain expressions out of his terminology and have been influ- 

 enced more or less directly by his ideas, particularly in regard to evolution. 

 But his great gift for form has also its darker side. He who saw in form the 

 true content of existence could not imagine a world to be other than finite — 

 spherical, for the sphere is the most perfect form — and as he could not visual- 

 ize an infinite world, he could not imagine infinite potentialities of knowl- 

 edge; on the contrary, he expressly declared that his own system, complete 

 as it was, would make it possible to solve all problems. But for that reason 

 he takes up all questions for discussion, even such as in our time would 

 be received with the old proverb "A fool can ask more than seven wise men 

 can answer." Often when reading his writings one can fancy that one hears 

 an inquisitive pupil offering objections which the master takes up with un- 

 disturbed calm and answers with unerring assurance in accordance with the 

 principles of his system; as, for instance, why men, and not women, be- 

 come bald; why the sow produces many pigs while the cow bears only one calf, 

 etc. The result is that, while the reader can sometimes trace in his writings 

 the pen of a biologist with almost a modern view of life's phenomena; on the 

 next page he may receive the impression of a master of scholastic disputation 

 from a mediaeval university. Many of the irregularities may certainly be due 

 to his treatises not having been carefully planned out; a number of them are 

 probably notes of lectures published by his pupils, and as such are perhaps 

 in places based on misapprehensions of the meaning of the lectures. 



To give a complete description of Aristotle's biological works would be 

 a voluminous task and would result in a wearisome mass of detail. In order, 

 however, to give some idea of the peculiarities of his work, a brief account 

 must here be given of his position as regards the various main sections of 

 biology. 



Aristotle's classification of animals 

 In regard to the classification of animals, Aristotle, as was hinted above, 

 has made an essentially important contribution to the subject by differentiat- 

 ing between and analysing and characterizing, from different points of view. 



