But the leading error common to them all, as I seem to see it, is their conception of society as a stable thing--a piece of machinery which must be properly “assembled,” as the engineers say; forgetful of the extraordinary discontinuity which inheres in the swift-approaching death of all its parts, and their replacement by helpless immaturity. The first fact of society really is that all its individuals are mortal. This we all know, but I question whether even Herbert Spencer fully reckoned with it; and certainly the common run of social speculators have not begun to realise what it means. Human life is made up of generations, and the key to all progress lies in the nature of the relation between one generation and another. Spencer records the case of an Oxford graduate, desirous to be his secretary, who did not know that the population of Great Britain is increasing. Here is a capital present fact of the--merely quantitative--relation between successive generations. So far as any influence on their theory or practice is concerned, it is still unknown to nearly all our advisers. Yet this fact of the ceaseless multiplication of man, which has distinguished him from the first, and is absolutely peculiar to him of all living species, animal or vegetable, as Sir E. Ray Lankester has lately pointed out, is the source of the major facts of history and the besetting condition of every social problem that can be named at this hour. The professional and dedicated teachers of morality seem to be in little better case. They believe in babies, perhaps, as the prime and only really valid source of the weal and wealth and strength of nations, and as the great moralisers and humanisers of the generation that gives them birth. They are beginning to join in that public outcry against infant mortality which will yet abolish this abominable stain upon our time. But they are lamentably uninformed. They do not know, for instance, that a high infant mortality habitually goes with a high birth-rate, not only in human society but in all living species; and they have yet to appreciate the proposition which I have so often advanced and which, to me at any rate, seems absolutely self-evident, that until we have learnt how to keep alive all the healthy babies now born--that is to say, not less than ninety per cent. of all, the babies in the slums included--it is monstrous to cry for more, _to be similarly slain_. These bewailings about our mercifully falling birth-rate, uncoupled with any attention to the slaughter of the children actually born, are pitiable in their blindness and would be lamentable if they had any effect--of which there is fortunately no sign whatever, but indeed the contrary.