The founder of modern Political Economy and, with Hume, the intellectual heart of the Scottish Enlightenment. Smith is often caricatured as the prophet of greedy self-interest, but that reading comes from reading one of his books and not the other. The Theory of Moral Sentiments (1759) grounds ethics in sympathy — our capacity to imaginatively inhabit one another's situations and feel an "impartial spectator's" judgment of our own conduct. The Wealth of Nations (1776) then describes how, within a framework of law and moral norms, market exchange harnesses self-interest to produce broad material improvement.
The "invisible hand" appears just once in Wealth of Nations, and Smith was sharply aware of what it could not do. He warned against the tendency of merchants to combine against the public, denounced the cruelty of the slave trade, and wrote unsparingly about how the division of labor could deaden the minds of workers. His political economy is inseparable from his moral psychology: markets work because people are socialized into habits of justice, not because atoms pursue utility.
Almost everything that came after — Classical Liberalism, Karl Marx's critique of it, and 20th-century debates about markets and morals — is a response to Smith.