Henry Sidgwick's The Methods of Ethics is one of the most important and influential works in the history of moral philosophy. The Methods of Ethics clarifies and tackles some of the most enduring and difficult problems of morality. It offers readers a high-calibre example of analytical moral philosophy. This Element interprets and critically evaluates select positions and arguments in Sidgwick's The Methods of Ethics. It focuses specifically on Sidgwick's moral epistemology, his argument against common-sense morality, his argument for utilitarianism, his argument for rational egoism, and his argument for what he calls 'the dualism of practical reason', the thesis that utilitarianism and rational egoism are coordinate but conflicting requirements of rationality. Sidgwick's Ethics attempts to acquaint readers with the scholarly and theoretical debates relating to Sidgwick's theses, while providing readers with a greater appreciation of the depth and sophistication of Sidgwick's masterpiece.