Capitalism allows private individuals and businesses, rather than the state, to invest money and resources into profitable commercial activities. Adam Smith was an early champion of capitalism, publishing "The Wealth of Nations" in 1776 which discussed key capitalist concepts like the law of supply and demand, division of labor, and using profits to generate more profits. While early forms of capitalism like mercantilism focused on countries controlling trade for economic gains, modern capitalism as practiced in the US allows for free market forces and has incorporated some socialist policies.