One is tempted to enquire, whether this ingenious explanation could be so modified as to apply not merely to individuals but to communities. Is it needful for the cause of civilisation as a whole, that the organised embodiment of each particular civilisation, if and when its free development is arrested, should make room for younger and more vigorous competitors? And if so can we find in Natural Selection the mechanism by which the principle of decay and dissolution shall be so implanted in the very nature of human associations that a due succession among them shall always be maintained? To this second question the answer must, I think, be in the negative. The struggle for existence between different races and different societies has admittedly played a great part in social development. But to extend Weismann’s idea from the organic to the social world, would imply a prolonged competition between groups of communities in which decadence was the rule, and groups in which it was not;--ending in the survival of the first, and the destruction of the second. The groups whose members suffered periodical decadence and dissolution would be the fittest to survive: just as, on Weismann’s theory, those species gain in competitive efficiency whom death has unburdened of the old. Few will say that in the petty fragment of human history which alone is open to our inspection, there is satisfactory evidence of any such long drawn process. Some may even be disposed to ask whether there is adequate evidence of such a phenomenon as decadence at all. And it must be acknowledged that the affirmative answer should be given with caution. Evidently we must not consider a diminution of national power, whether relative or absolute, as constituting by itself a proof of national decadence. Holland is not decadent because her place in the hierarchy of European Powers is less exalted than it was two hundred and fifty years ago. Spain was not necessarily decadent at the end of the seventeenth century because she had exhausted herself in a contest far beyond her resources either in money or in men. It would, I think, be rash even to say that Venice was decadent at the end of the eighteenth century, though the growth of other Powers, and the diversion of the great trade routes, had shorn her of wealth and international influence. These are misfortunes which in the sphere of sociology correspond to accident or disease in the sphere of biology. And what we are concerned to know is whether in the sphere of sociology there is also anything corresponding to the decay of old age--a decay which may be hastened by accident or disease, which must be ended by accident or disease, but is certainly to be distinguished from both.