 In Helvétius’ account “interest” lies at the epicentre of moral science, but Bentham recognised that the concept only had meaning, like other fictitious entities in ethics such as “desire” and “motive”, when redefined in terms of the avoidance of pains and acquisition of pleasures (1970, 12; 1838–43, VIII, 290). In general he followed Adam Smith in believing the individual to be the best judge of his or her own interests, but the simplicity of this proposition is deceptive (see Engelmann 2001).