2. We have already seen in our first chapter the proofs of the proposition, that the Value of anything whatsoever bought and sold is determined by the Demand for it and the Supply of it then and there present. Also we have now seen at considerable length the main phases and grounds of the Demand for each of the three classes of Personal services bought and sold among men. The next topic in order is the Supply of personal services in the various markets. Here it will not be necessary to distinguish particularly the three classes of Services, inasmuch as the circumstances governing the Supply in each are substantially similar. In Economics generally we have to deal chiefly with Persons, and only subordinately with Things; when we come to the Supply of personal services, answering to the Demand for them on the part of other persons, this point becomes conspicuous; and it is here, if anywhere, within the realm of our science, that we need to devote a word to a singular doctrine, that has been famous for nearly a century under the term of _Malthusianism_. Thomas Robert Malthus, 1766-1836, was an English clergyman and teacher, a wide traveller and keen observer of men, one who divided his time during a long life between cure and chair and the libraries of the Universities, published in 1798 his "_Essay on the Principles of Population as it affects the Future Improvement of Society_"; in this and in subsequent editions enlarged and enriched, he brought out with its proofs the core of his startling pronouncement, that the human race is found to increase in numbers in something like geometrical progression, while the means of subsistence for them on any given area of agriculture can only increase in something like arithmetical proportion; the United States was then doubling its population in 25 years, and he calculated that, at this rate, the inhabitants of any country in five centuries would increase to above a million times their present number, which would give England in that time more than twenty million millions of people, or more than could even get standing-room there; for this natural tendency of the law of human fecundity to outstrip the results of the law of returns from land, he saw no remedy except in checks to population, which he divided into _the positive_ and _the preventive_, the first of which, such as war and famine and disease, increase the annual number of deaths; and the second of which, such as prudence in contracting marriage and temperance after marriage, diminish the number of births; and Malthus and his followers, among whom the famous Thomas Chalmers was prominent, were at great pains to inculcate upon the laboring classes the duty of later marriages and fewer children, as an indispensable condition of their rise in comforts, and of "the future improvement of Society."