Among all the several species of psychological entities, the names of which are to be found either in the Table of the Springs of Action, or in the Explanations above subjoined to it, the two which are as it were the roots, the main pillars or foundations of all the rest, the matter of which all the rest are composed—or the receptacles of that matter, which soever may be the physical image, employed to give aid, if not existence to conception, will be, it is believed, if they have not been already, seem to be PLEASURES and PAINS. Of these, the existence is matter of universal and constant experience. Without any of the rest, these are susceptible of,—and as often as they come unlooked for, do actually come into, existence: without these, no one of all those others ever had, or ever could have had, existence.

Jeremy Bentham, Deontology Together with A Table of the Springs of Action and Article on Utilitarianism, Oxford, 1983, p. 98