utilitarianism (yōō´tĬlĬtr´ēənĬzəm, yōōtĬ´–), in ethics, the theory that the rightness or wrongness of an action is determined by its usefulness in bringing about the most happiness of all those affected by it. Utilitarianism is a form of consequentialism, which advocates that those actions are right which bring about the most good overall. Jeremy Bentham identified good consequences with pleasure, which is measured in terms of intensity, duration, certainty, propinquity, fecundity, purity, and extent. John Stuart Mill argued that pleasures differ in quality as well as quantity and that the highest good involves the highest quality as well as quantity of pleasure. Herbert Spencer developed an evolutionary utilitarian ethics in which the principles of ethical living are based on the evolutionary changes of organic development. G. E. Moore, in his Principia Ethica (1903), presented a version of utilitarianism in which he rejected the traditional equating of good with pleasure. Later in the 20th cent., versions of utilitarianism have been propounded by J. J. C. Smart and R. M. Hare.
See J. J. C. Smart and B. Williams, Utilitarianism (1973); A. Sen and B. Williams, ed., Utilitarianism and Beyond (1982).