Adam Smith's 1776 investigation into the causes of national prosperity -- the foundational text of modern economics, which established that markets coordinate economic activity more effectively than government direction, and whose arguments have been used to justify both the free market policies it recommends and the social concerns it actually expresses.
Adam Smith wrote a thousand-page book arguing that nations become wealthy not through the accumulation of gold or government direction but through the division of labor and free exchange. He is remembered as the prophet of capitalism. He also argued for progressive taxation, public education funded by the state, and deep suspicion of businessmen who use political influence to protect their profits. The capitalism that claims him has selectively read him.