The tendency in the races of history has been to over-population, or to a population beyond the food supply, and there is probably no race known to history that did not at some one period of its rise or fall suffer from over-population.
States have mostly been concerned, therefore, with restraining or inhibiting the natural reproductive instinct of their subjects through marriage laws which protect the State, by fixing paternal responsibility. There were strong reasons why a State should not be over-populated, and only one reason why it should not be under-populated. That one reason was the danger of annihilation from invasion.
Sparta was said to have suffered thus, because of under-population, and passed a law encouraging large families. Alexander encouraged his soldiers to intermarry with the women of conquered races, in order to diminish racial differences and antagonism, and Augustus framed laws for the discouragement of celibacy, but no law has ever been passed decreeing that individuals must mate, or if they do mate that they shall procreate.
Malthus, the great and good philanthropist of Harleybury, a great moralist and Christian clergyman, urged that it was people's duty not to mate and procreate until they had reasonable hope of being able easily to rear, support, and educate the normal family of four, and, if that were impossible, not to mate at all. As a Christian clergyman, Malthus did not interpret the Divine command apart from the consequences of its literal acceptance.
"Be fruitful," meant to Malthus reproduce your kind,—that implied not only bringing babies into the world, but rearing them up to healthy, robust, and prosperous manhood, with every prospect of continuing the process.
"Multiply and replenish the earth" as a command to Noah, meant in the mind of the Rector of Harleybury, "People the earth with men after your own image."
Very little care would be required in Noah's time, with his fine alluvial flats, and sparse population, but in Malthus's time the command could not be fully carried out without labour, self-development, and "moral restraint."
The physiological law is simple and blind, taking no cognisance of the consequences, or the quality of the offspring produced. The divine command is complex. It embodies the reproductive instinct, but restrains and guides it in view of ultimate consequences.
So much for the views and teaching of Malthus. To him no ethical standard was violated in preventing offspring by protracted continence, or lifelong celibacy, provided the motive was the inability so to provide for a family as to require no aid from the state. And it is difficult to escape this conclusion. There is no ethical, Christian, or social law, that directs a man or woman to procreate their kind if they cannot, or have reasonable grounds to think they cannot, support their offspring without aid from others.
There can be, therefore, no just law that decrees that men or women shall marry under such circumstances. In fact most philanthropists think they violate a social and ethical law if they do marry.