Misery is caused by poverty, or the need of food or clothing, and is thus proportionate to the means of subsistence. As the means of subsistence are abundant, misery will be less, the death-rate lower, and _caeteris paribus_ the birth-rate higher. The increase will be directly proportional to the means of subsistence. Vice as a check to increase, is common to civilized and savage man, and limits population by artificial checks to conception, abortion, infanticide, disease, and war. The third check, moral restraint, is peculiar to civilized man, and in the writings of Malthus, consists in restraint from marriage or simply delayed marriage. Bonar says (Malthus and his Work, p. 53), "Moral restraint in the pages of Malthus, simply means continence which is abstinence from marriage followed by no irregularities." These checks have their origin in a need for, and scarcity of food,--food comprising all those conditions necessary to healthy life. The need of food is vital and permanent. The desire for food, immediate and prospective, is the first motive of all animal activity, but the amount of food available in the world is limited, and the possible increase of food is estimated by Malthus at an arithmetical ratio. Whether or not this is an accurate estimate of the ratio of food increase is immaterial. Malthus's famous progressions, the geometrical ratio of increase in the case of animals, and the arithmetical ratio of increase in the case of food, contain the vital and irrefutable truth of the immense disproportion between the power of reproduction in man and the power of production in food. Under the normal conditions of life, the population tends constantly to press upon, and is restrained by the limits of food. The true significance of the word _tends_ must not be overlooked, or a similar fallacy to that of Nitti's will occur, when he overlooked the significance of the term "power to multiply." It is perfectly true to say, that population _tends_ to press upon the limits of subsistence, and unrestrained by moral means or man's reason actually does so. Some social writers appear to think that, if they can show that production has far outstripped population, that, in other words, population for the last fifty years at least has _not_ pressed upon the limits of food, Malthus by that fact is refuted.