Utilitarianism is an empirical philosophy (requiring a calculation) derived from the idea that pleasure or happiness is the one intrinsic good. The three major branches, outlined below, work in a slightly different way: Mill stresses general rules of thumb, Bentham a hedonic individual assessment of the utility of actions, and Singer side-steps the philosophical problems with pleasure by stressing choice (preference) and interests. Since Urmson (1953) Mill has been described as a weak rule utilitarian – but we need to clarify what these terms mean – the ‘weakness’ comes from the fact that Mill argues that when moral dilemmas occur, we should revert to being act utilitarians and exercise our judgement.