Abstract

Taking ‘what ought to be’ to include both what is commonly judged to be ‘good’ and what is commonly judged to be ‘right’, that is to say, ‘the duty’ of a person, Sidgwick observes that there is a rationally based recognition of the variation in people's duties. Given the failure of people on many occasions to do their duty, we must acknowledge that ‘what ought to be’ to a large degree ‘is not’, and that the former is independent of whether it comes into being. Sidgwick asks if this distinction is ultimate and irreducible. He argues that, although no answer can be provided by considering moral judgements from a psychological or sociological viewpoint, adopting a philosophical or epistemological perspective may allow for the reduction between ‘what is’ and ‘what ought to be’, as this perspective takes both duty and facts to be objects of thought, or knowledge, that exhibit similar relations in thought, relations like that between the universal and the particular, and between inductive method and deductive method.