civilised men and women living in an advanced state of society and
seeking, if we can, to advance that state of society still further.

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.