The result, both for individuals and communities, is that a selection of ideas instead of a selection of organic units can to an ever greater extent take place; and thus the actual extinction of living matter be increasingly avoided. For instance, we find the substitution of judicial procedure, in which the ideas of two disputants about the matter in dispute are weighed and a selection made in favour of one, for various forms of violence and combat in which one or other of the actual disputants was often eliminated. Or again, in struggles between communities, even though warfare is still resorted to, yet it does not operate in the same way as in earlier stages of human evolution. A salient example of this is afforded by the result of the recent war to Germany; although an equally good instance can be seen, for example, in the Boer War. In primitive wars, the defeated tribe was wherever possible exterminated or enslaved: it ceased to exist as an independent unit, and the great majority of its male members were killed. This is impossible under present conditions: and all those who preserve, or have ever possessed, any political sanity aim, for instance, neither at the physical nor the economic destruction or subordination of Germany, but--to use one of those attractive catchwords that sounded so well in war-time--at her “change of heart”--in other words, the extermination, not of a nation, but of a national tradition. To what extent this substitution of mental for physical will continue it is hard to say; already, to take another field, the multiplication of cheap books has led to an ever increasing number of men and women finding most of their adventure and romance in books instead of in the life that we are accustomed to call real. But that would lead us away from our main point--enough to have indicated another great difference between processes above and below the human level. There are numerous important questions concerning our right to apply biological ideas of heredity directly to human beings which I would have liked to touch upon. But for one thing I have not the time, and for another, Mr. Carr-Saunders in his recent book on the Population Problem has dealt so fully with the relation between biological inheritance and what may be called tradition-inheritance, that I omit them with a good conscience. In this brief treatment I have had to ask you to take conclusions on trust, without presenting the evidence on which they are based; this, however, is inevitable when transferring ideas from one science to another. I have attempted to show, first, that biology can profit by incorporating certain conclusions of sociology and so rounding off and completing certain of its own principles: on the other hand, I have put before you my belief that there are certain basic biological principles which must be taken into account by the sociologist--principles which hold good in sociology because man too is an organism.