Utilitarianism can be understood as a movement for legal, political and social reform that flourished in the first half of the nineteenth century, or, again, as the ideology of that movement. But it is also, and more persistently, a general ethical theory and it is almost exclusively in this sense that I shall be concerned with it. As a theory of ethics it provides a criterion for distinguishing between right and wrong action and, by implication, an account of the nature of the moral judgements that characterise action as right or wrong.