The primary end of marriage is to beget and bear offspring, and to rear them until they are able to take care of themselves. On that basis Man is at one with all the mammals and most of the birds. If, indeed, we disregard the originally less essential part of this end,—that is to say, the care and tending of the young,—this end of marriage is not only the primary but usually the sole end of sexual intercourse in the whole mammal world. As a natural instinct, its achievement involves gratification and well-being, but this bait of gratification is merely a device of Nature’s and not in itself an end having any useful function at the periods when conception is not possible. This is clearly indicated by the fact that among animals the female only experiences sexual desire at the season of impregnation, and that desire ceases as soon as impregnation takes place, though this is only in a few species true of the male, obviously because, if his sexual desire and aptitude were confined to so brief a period, the chances of the female meeting the right male at the right moment would be too seriously diminished; so that the attentive and inquisitive attitude towards the female by the male animal—which we may often think we see still traceable in the human species—is not the outcome of lustfulness for personal gratification (“wantonly to satisfy carnal lusts and appetites like brute beasts,” as the Anglican Prayer Book incorrectly puts it) but implanted by Nature for the benefit of the female and the attainment of the primary object of procreation. This primary object we may term the animal end of marriage. This object remains not only the primary but even the sole end of marriage among the lower races of mankind generally. The erotic idea in its deeper sense, that is to say the element of love, arose very slowly in mankind. It is found, it is true, among some lower races, and it appears that some tribes possess a word for the joy of love in a purely psychic sense. But even among European races the evolution was late. The Greek poets, except the latest, showed little recognition of love as an element of marriage. Theognis compared marriage with cattle-breeding. The Romans of the Republic took much the same view. Greeks and Romans alike regarded breeding as the one recognizable object of marriage; any other object was mere wantonness and had better, they thought, be carried on outside marriage. Religion, which preserves so many ancient and primitive conceptions of life, has consecrated this conception also, and Christianity—though, as I will point out later, it has tended to enlarge the conception—at the outset only offered the choice between celibacy on the one hand and on the other marriage for the production of offspring.