It is necessary to make allowance for variations, thereby shunning the extreme theorists who insist on moulding all facts to their theories, but we may conclude that—­as the approximately equal number of the sexes indicates—­in the human species, as among many of the higher animals, a more or less permanent monogamy has on the whole tended to prevail.  That is a fact of great significance in its implications.  For we have to realize that we are here in the presence of a natural fact.  Sexual relationships, in human as in animal societies, follow a natural law, oscillating on each side of the norm, and there is no place for the theory that that law was imposed artificially.  If all artificial “laws” could be abolished the natural order of the sexual relationships would continue to subsist substantially as at present.  Virtue, said Cicero, is but Nature carried out to the utmost.  Or, as Holbach put it, arguing that our institutions tend whither Nature tends, “art is only Nature acting by the help of the instruments she has herself made.”  Shakespeare had already seen much the same truth when he said that the art which adds to Nature “is an art that Nature makes.”  Law and religion have buttressed monogamy; it is not based on them but on the needs and customs of mankind, and these constitute its completely adequate sanctions.[313] Or, as Cope put it, marriage is not the creation of law but the law is its creation.[314] Crawley, again, throughout his study of primitive sex relationships, emphasizes the fact that our formal marriage system is not, as so many religious and moral writers once supposed, a forcible repression of natural impulses, but merely the rigid crystallization of those natural impulses, which in a more fluid form have been in human nature from the first.  Our conventional forms, we must believe, have not introduced any elements of value, while in some respects they have been mischievous.

It is necessary to bear in mind that the conclusion that monogamic marriage is natural, and represents an order which is in harmony with the instincts of the majority of people, by no means involves agreement with the details of any particular legal system of monogamy.  Monogamic marriage is a natural biological fact, alike in many animals and in man.  But no system of legal regulation is a natural biological fact.  When a highly esteemed alienist, Dr. Clouston, writes (The Hygiene of Mind, p. 245) “there is only one natural mode of gratifying sexual nisus and reproductive instinct, that of marriage,” the statement requires considerable exegesis before it can be accepted, or even receive an intelligible meaning, and if we are to understand by “marriage” the particular form and implications of the English marriage law, or even of the somewhat more enlightened Scotch law, the statement is absolutely false.  There is a world of difference, as J.A.  Godfrey remarks (The Science of Sex, 1901, p. 278), between natural monogamous marriage and our legal