The Theory of Moral Sentiments

Smith's first book, drawn from his moral philosophy lectures at Glasgow and revised several times, most heavily for the sixth edition of 1790. It explains moral judgement through sympathy: by imagining ourselves in another's situation we come to share, in weaker form, what they feel, and we approve of their feelings when they match what we would feel. Propriety, merit and demerit are built on this. To judge ourselves we imagine an impartial spectator, who becomes the voice of conscience. Smith examines how luck affects praise and blame, why we admire wealth and greatness more than wisdom and virtue, and how custom and fashion bend moral feeling. Part IV, on utility, contains the book's one use of the phrase 'invisible hand'. Part VI, added in 1790, discusses prudence, benevolence and self-command, and warns against the 'man of system' who would arrange citizens like pieces on a chessboard. Part VII surveys earlier moral theories.

It shows the author of The Wealth of Nations as a moral psychologist, and its account of sympathy and the impartial spectator is still used in ethics and in research on empathy.