The Laws of the Growth of Population.--Can the growth of population be reduced to any principle or law? This is a problem which has puzzled social thinkers for a long time. Many have thought that the growth of population can be reduced to one or more relatively simple laws, but we have seen from analyzing the statistics of birth rate and death rate that this is hardly probable. A formula that would cover the growth of population would have to cover all of the variable causes influencing birth rate and death rate and so entering into the surplus of births over deaths. It is evident that these causes are too complex to be reduced to any such formula among modern civilized peoples. In the animal world and among uncivilized peoples, however, conditions are quite different, and the growth of population is regulated by certain very simple principles or laws. Thus it is probable that for centuries before the whites came, the Indians of North America were stationary in their population, for the reason that under their stationary condition of culture a given area could support only so many people. In conditions of savagery, and even of barbarism, therefore, we can lay down the principle that population will increase up to the limit of food supply, will stop there and remain stationary until food supply increases. This is the condition which governs the growth of the population of all animal species, and, as we have already said, of the savages and barbarians among the human species. But among civilized men who have attempted the control of physical nature, and to some extent even the control of human nature, many other factors enter in to influence both birth rate and death rate, and so the growth of the population. Nevertheless, many social thinkers of the past have conceived, as has already been said, that the growth of population might be reduced to very simple and definite laws. Among the first who proposed laws governing population was an English economist, Thomas Robert Malthus, whose active career coincides with the first quarter of the nineteenth century. In 1798 Malthus put forth a little book which he entitled _An Essay on the Principle of Population as it affects the future improvement of society_. This essay went through numerous editions and revisions, and in it Malthus elaborated his famous economic theory of the growth of population. Inasmuch as this theory of Malthus has been the storm center of sociological and economic writers for the past one hundred years, it is worth our while to note very briefly what Malthus's theory was, and why it is inadequate as a scientific statement of the laws governing the growth of population.