84 ESSAYS OF A BIOLOGIST 



A man can pass from one occupation to another. 

 He can be specialized for several, or combine a high 

 degree of professional skill in one with the generalized 

 knowledge of an amateur in another. It is this 

 obvious but fundamental fact which is at the bottom 

 of many of the failures to apply biological ideas to 

 sociology. 



Another human distinction is the increase of the 

 part played by environment in man as opposed to 

 animals (in determining hisbiologically effective nature). 

 Environment plays not merely a large part, but a 

 preponderating one, in his development after the first 

 year or so of his life. Tradition provides a special 

 environment, made by man for man's own develop- 

 ment ; and men brought up in markedly different 

 traditions arrive at different end-results just as surely 

 and obviously as do men of markedly different heredi- 

 tary tendencies arrive at different end-results even 

 though exposed to similar traditions. Traditions are 

 infinitely complex things : there are world-traditions, 

 national traditions broad and narrow, class traditions 

 and traditions of profession and trade, traditions of 

 predilection, of art, of religion : and men may be 

 exposed in their development to the combined influence 

 of a number of these. But the nett result of the 

 diversity of tradition is an extraordinary diversity of 

 end-result. ^Nihil humanum alienum a me puto ' 

 — Terence could only say this with truth in the sense 

 that there are certain fundamental emotions and 



