Utilitarianism is a consequentialist ethical theory holding that the best action is the one that maximizes overall utility, typically understood as happiness, well-being, or the satisfaction of preferences for the greatest number of people. Classical utilitarianism was founded by Jeremy Bentham in his work An Introduction to the Principles of Morals and Legislation (1789), where he introduced the principle of utility as a standard for evaluating laws and actions. To operationalize this principle, Bentham developed the felicific calculus (also called the hedonic calculus), a method for measuring the pleasure and pain produced by an action using criteria such as intensity, duration, certainty, propinquity, fecundity, purity, and extent. By summing these values, Bentham believed any action could be quantitatively assessed for its contribution to overall happiness.
John Stuart Mill modified Bentham's framework by introducing a qualitative distinction between pleasures. Mill argued that intellectual and moral pleasures, which he called higher pleasures, are inherently superior to mere physical or lower pleasures, even if the latter are more intense in quantity. This refinement responded to objections that Bentham's calculus could not distinguish between a sophisticated symphony and a simple game of pushpin. Beyond classical hedonic utilitarianism, preference utilitarianism, associated with philosophers such as R.M. Hare and Peter Singer, defines the good as the satisfaction of people's preferences or interests rather than the maximization of pleasure. The theory also branches into act utilitarianism, which evaluates each individual action by its consequences, and rule utilitarianism, which assesses actions according to whether they follow rules that, when generally adopted, maximize utility.
Despite its intuitive appeal, utilitarianism faces significant criticisms. A major concern is that the theory can justify sacrificing the rights of a minority if doing so maximizes overall happiness, conflicting with intuitions about individual rights and justice. Robert Nozick introduced the utility monster thought experiment to expose a related flaw: a being that derives enormously more pleasure from resources than others would, under utilitarianism, be entitled to nearly everything, revealing the theory's potential to demand extreme redistribution. John Rawls and others have raised the separateness of persons objection, arguing that utilitarianism treats individuals as mere vessels for aggregating utility rather than as distinct moral agents with their own claims. Each of these challenges targets a different aspect of utilitarian reasoning, yet none has decisively overturned the theory, and it remains one of the most influential frameworks in moral philosophy.