The obligation to promote the happiness of the greatest number Bentham called the principle of utility. In the manner of the eighteenth century, he frankly admitted that this first principle of his philosophy cannot be proved, because a chain of proof must begin somewhere, and there can be no principle higher than a first principle. The principle, he said, is part of “the natural constitution of the human frame,” and people embrace it spontaneously in judging others if not in directing their own actions. Bentham believed that, in addition to this principle, there are in humans social motives, including “goodwill” or “benevolence,” which work in harmony with the principle of utility; but the inclination to kindness is one thing and the principle of utility something else. The latter is an intelligible rule that lies at the foundation of all morals; hence, also of legislation.
What chiefly distinguished Bentham from other eighteenth century moral philosophers was, first, that he recognized only one ultimate principle of morals and, second, that the principle that he maintained was one that admitted of empirical application. The Age of Reason commonly appealed to a whole array of self-evident principles, intuitive convictions, and laws of nature. However, Bentham complained that none of them provided an external standard on which people could agree. In many instances, the alleged truths of nature were an expression of the principle of utility, but at other times they were nothing but expressions of private feelings, prejudices, and interests. The principle of utility, on the other hand, made it possible to define good and evil, right and wrong, in terms that everyone understood and accepted.Nature has placed mankind under the governance of two sovereign masters, pain and pleasure. . . . The principle of utility recognizes this subjection, and assumes it for the foundation of that system, the object of which is to rear the fabric of felicity by the hands of reason and of law.
These fundamentals having been laid down, Bentham devoted the remainder of his work to detailed analyses of the psychology of human behavior, chiefly as it bears on problems of social control. His aim was to find the natural divisions of his subject and to arrange the matter in tables that would be of help in drawing inductions.