"The Theory of Moral Sentiments" is a book written by Adam Smith, a Scottish philosopher and economist who lived from 1723 to 1790. First published in 1759, the book is considered one of the most important works in the field of moral philosophy.

In the book, Smith explores the nature of morality and the role of sympathy and empathy in human interactions. He argues that human beings are naturally inclined to feel sympathy for others, and that this sympathy forms the basis of moral judgments. He also discusses the concept of the "impartial spectator," an imagined observer who helps us to judge the morality of our own actions.

Smith's ideas in "The Theory of Moral Sentiments" have had a profound impact on fields beyond moral philosophy, including economics and political theory. In his later work, "The Wealth of Nations," Smith developed his ideas on the nature of markets and the division of labor, which have become foundational concepts in modern economics.

Overall, "The Theory of Moral Sentiments" is a key work in the development of Western moral philosophy, and is still widely studied and debated today.