A moral theory according to which an action is right if and only if it conforms to the principle of utility. Bentham formulated the principle of utility as part of such a theory in Introduction to the Principles of Morals and Legislation in 1789. An action conforms to the principle of utility if and only if its performance will be more productive of pleasure or happiness, or more preventive of pain or unhappiness, than any alternative. Instead of 'pleasure' and 'happiness' the word 'welfare' is also apt: the value of the consequences of an action is determined solely by the welfare of individuals.
A characteristic feature of Bentham's theory is the idea that the rightness of an action entirely depends on the value of its consequences. This is why the theory is also described as consequentialist. Bentham's theory differs from certain other varieties of utilitarianism (or consequentialism) by its distinctive assumption that the standard of value is pleasure and the absence of pain; by being an act-utilitarian; and by its maximising assumption that an action is not right unless it tends towards the optimal outcome.
The view that utilitarianism is unable to accommodate any values except the crass, gross or materialistic ones is mistaken.
Since the 1960s, many writers have used consequentialism instead of utilitarianism for the view that the rightness of an action entirely depends on the value of its consequences. Many writers now restrict the word utilitarianism to denote certain kinds of consequentialism, especially Bentham's and Mill's. Currently there is terminological diversity, and the varieties of utilitarianism mentioned elsewhere are varieties of consequentialism.
The Penguin Dictionary of Philosophy