glanced at. And yet this third may contain the true solution of the difficult problem, and through its active operation the geometrical increase of Malthus may, perhaps, be succeeded by a stationary condition of human population.
By the physical check we mean the effect of all the forces which act from outside upon the individual—such agencies as war, famine, pestilence, exposure, climatic changes, and all similar destructive influences. The mental check refers to influences proceeding from the mind of the individual. It is what is usually called the prudential check, through which individuals wisely decline to bring into the world children who must be exposed to inevitable misery, or governments restrain injudicious marriages by enactments looking to the same end. The physiological check is also internal in its origin, but not voluntary. It consists of that limit to human fecundity which is caused by employment of the organic forces in other directions.
Of these three checks to population the second only is fully under the control of the individual himself. The physical check largely arises from the action of other individuals, such as the war-making powers. It also largely flows from the hostile energies of Nature, and may, in this direction, be partly set aside by individual effort, through attention to the laws of health, and prudent avoidance of injurious conditions. The physiological check is beyond the reach of the will. It is a natural effect of human development, needs no forced restraint from marriage for its operation, and is consistent with the most natural and desirable of human relations.
Of the three checks to population here named, we will, in this paper, consider only the physiological. The others have been written upon so abundantly that there is little new to be said concerning them. It will suffice here to remark that the physical check—that which acts through the agency of famine, violence, disease, and similar influences—has ruled almost supreme in the past ages of the world, and is still vigorously active upon the great mass of mankind. The prudential check, which acts through forced desistance from marriage and childbearing, is now actively effective in several of the more advanced European nations, probably most fully in France, and has gone far toward negativing the action of the Malthusian law. The physiological check, which we have here to consider, has also been somewhat effective in the past, but its highest influences are only now coming into play, and it promises to become an efficient and desirable agent in hindering the undue increase of human population in the future.
The principle to which we here allude has been very greatly neglected by writers on the subject of population. Those who have dealt with it have done so only cursorily, and have failed to consider it in all its bearings. It is therefore a problem that is open to further investigation. And in entering upon this inquiry it is necessary to
