They believed that promoting human happiness was incumbent on us since it was approved by God. Yet further, absolute interpretations of rules seem highly counter-intuitive, and yet we need some justification for any exceptions — provided, again, by utilitarianism.
One also considers extent — the number of people affected by the action. His most important theoretical work is the Introduction to the Principles of Morals and Legislationin which much of his moral theory—which he said reflected "the greatest happiness principle"—is described and developed.
Egoism: Though Bentham is an advocate of altruistic Hedonism, he clearly recognizes the natural egoism of man.
In fact, the ideal cannot be evolved from the actual. In fact, Bentham holds that people have always lived in society, and so there can be no state of nature though he does distinguish between political society and "natural society" and no "social contract" a notion which he held was not only unhistorical but pernicious.
It is an account of its existence that no man would consent to be changed into any of the lower animals capable of sensual pleasure alone. From the hedonistic standpoint, it is not justifiable. A pleasure is pure, according to Bentham, when it is unmixed with pain.
To begin with, Bentham's moral philosophy reflects what he calls at different times "the greatest happiness principle" or "the principle of utility"—a term which he borrows from Hume. Recall that Bentham was enormously interested in social reform.
Bentham's moral philosophy, then, clearly reflects his psychological view that the primary motivators in human beings are pleasure and pain. At his death in London, on June 6,Bentham left literally tens of thousands of manuscript pages—some of which was work only sketched out, but all of which he hoped would be prepared for publication.
Hume also focused on character evaluation in his system.