Another human distinction is the increase of the part played by environment in man as opposed to animals (in determining his biologically 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 development; and men brought up in markedly different traditions arrive at different end-results just as surely and obviously as do men of markedly different hereditary 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 net 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 instincts found in all men, and also certain aspects of environment shared by all humanity--the sun and moon, earth, water, and fire, space and time, parents and society, and so on and so forth. I make no apologies for the length of this preliminary analysis, since it is precisely by the neglect of preliminary analysis that most attempts to correlate biology and sociology have failed. The salient fact emerges that with man there has been a radical change in evolutionary method. As space is limited, I am here only proposing to consider three of the chief contributions which biology can make to sociology--on the idea of progress, on the relation between individual and community, and on the applicability of the doctrine of the struggle for existence to man. As regards the idea of progress, biology can make a clear and unequivocal contribution: whereas man is biologically so young, his evolution is yet so chaotic and divergently directed, that it is very hard to arrive at definite conclusions from the study of his history alone. It has been a source of constant surprise to me that more use has not been made of biological data in the controversy over this question. In the little book recently edited by Mr. Marvin on various aspects of the concept of Progress, there was no article dealing with biological progress; and even in Professor Bury’s notable book, _The Idea of Progress_, biology was as little and as unsatisfactorily drawn upon as in Dean Inge’s writings on the subject. We have already seen that a certain direction obtains in organic evolution. Into the details of this process I have not here the time to go; we must be content with the brief enumeration which has already been given of the qualities of organisms whose maximum level, and to a lesser degree whose average, have increased during evolution.