The combined philosophy of the Greeks counselled the encouragement of the best citizens to increase their kind, and the practice of the exposure of infants and abortion.

A century of debate has raged round the name of Malthus, the great modern analyst of the population problem.  He published his first essay on population in 1798, a modest pamphlet, which fed so voraciously on the criticism supplied to it, that it developed into a mighty contribution to a great social problem, second only in time and in honour to the work of his great predecessor in economic studies, Adam Smith.

Malthus’s first essay defined and described the laws of multiplication as they apply only to the lower animals and savage man.  It was only in his revised work, published five years later, that he described moral restraint as a third check to population.

Adverse criticism had been bitter and severe, and Malthus saw that his first work had been premature.  He went to the continent to study the problem from personal observation in different countries.  He profited by his observation, and by the writings of his critics, and published his matured work in 1803.

The distinguishing feature about this edition was the addition of moral restraint as a check, to the two already described, vice and misery.

Malthus maintained that population has the power of doubling itself every 25 years.  Not that it does so, or had done so, or will do so, but that it is capable of doing so, and he instanced the American Colonies to prove this statement.

One would scarcely think it was necessary to enforce this distinction, between what population has done, or is doing, and what it is capable of doing.  But when social writers, like Francesco Nitti (Population and the Social System, p. 90), urge as an argument against Malthus’s position that, if his principles were true, a population of 176,000,000 in the year 1800 would have required a population of only one in the time of our Saviour, it is necessary to insist upon the difference between increase and the power of increase.

One specific instance of this doubling process is sufficient to prove the power of increase possessed by a community, and the instance of the American Colonies, cited by Malthus, has never been denied.

A doubling of population in 25 years was thus looked upon by Malthus as the normal increase, under the most favourable conditions; but the checks to increase, vice, misery, and moral restraint are operative in varying degrees of intensity in civilized communities, and these may limit the doubling to once in 50, or once in 100 years, stop it altogether, or even sweep a nation from the face of the earth.

The natural increase among the lower animals is limited by misery only, in savage man by vice and misery only, and in civilized man by misery, vice, and moral restraint.