The "Theory of Population" (published in 1852), which is founded on the theory of an antagonism between the intellectual and the reproductive powers, and on the ancient theory of a direct relation between skull-capacity or brain-size and intellectual power, contains this passage: "From the beginning, pressure of population has been the proximate cause of progress. It produced the original diffusion of the race. It compelled men to abandon predatory habits and take to agriculture. It led to the clearing of the earth's surface. It forced men into the social state; made social organization inevitable; and has developed the social sentiments. It has stimulated to progressive improvements in production, and to increased skill and intelligence. It is daily pressing us into closer contact and more mutually dependent relationships. And after having caused, as it ultimately must, the due peopling of the globe, and the bringing of all its habitable parts into the highest state of culture,--after having brought all processes for the satisfaction of human wants to the greatest perfection,--after having, at the same time, developed the intellect into complete competency for its work, and the feelings into complete fitness for social life,--after having done all this, we see the pressure of population, as it gradually finishes its work, must gradually bring itself to an end." In a letter to Mr. Mill, published in Bain's "Mental and Moral Science" (p. 721, 3d edition), Spencer repudiates the title of Anti-Utilitarian, which Mr. Mill, in view of the criticisms of Utilitarianism contained in "Social Statics," had applied to him. He defines his position in respect to Utilitarianism as follows: "I have never regarded myself as an Anti-Utilitarian. My dissent from the doctrine of Utility as commonly understood, concerns, not the object to be reached by men, but the method of reaching it. While I admit that happiness is the ultimate end to be contemplated, I do not admit that it should be the proximate end. The Expediency Philosophy, having concluded that happiness is a thing to be achieved, assumes that Morality has no other business than empirically to generalize the results of conduct, and to supply for the guidance of conduct nothing more than its empirical generalizations.