A theory of capitalism describes the essential features of capitalism and how it functions. The history of various such theories is the subject of this article. Overview Conceptions of what constitutes capitalism have changed significantly over time, as well as being dependent on the political perspective and analytical approach adopted by the observer in question. Adam Smith focused on the role of enlightened self-interest (the "invisible hand") and the role of specialization in promoting the efficiency of capital accumulation. Ayn Rand defined capitalism as a social system based on the recognition of individual rights, including property rights, in which all property is privately owned, and called it the unknown ideal. Robert LeFevre, an American libertarian and primary theorist of autarchism, defined capitalism as savings and capital—in essence—as savings made by men, which are then invested in the tools of production. Some proponents of capitalism (like Milton Friedman) emphasize the role of free markets, which, they claim, promote freedom and democracy. For many (like Immanuel Wallerstein), capitalism hinges on the extension into a global dimension of an economic system in which goods and services are traded in markets and capital goods belong to non-state entities. For others (like Karl Marx), it is defined by the creation of a labor market in which most people must sell their labor power in order to make a living. Marx, along with others like Hilaire Belloc, also argued that capitalism differs from other market economies that feature private ownership because it features the concentration of the means of production in the hands of a few. Adam Smith Adam Smith is considered the first theorist of what we commonly refer to as capitalism. His 1776 work, An Inquiry into the Nature and Causes of the Wealth of Nations, theorized that within a given stable system of commerce and evaluation, individuals would respond to the incentive of earning more by specializing their production. These individuals would naturally, without specific state intervention, "direct ... that industry in such a manner as its produce may be of the greatest value." This would enable the whole economy to become more productive, and it would therefore be wealthier. Smith argued that protecting particular producers would lead to inefficient production, and that a national hoarding of specie (i.e. cash in the form of coinage) would only increase prices, in an argument similar to that advanced by David Hume. His systematic treatment of