The invisible hand is a metaphor inspired by the Scottish economist and moral philosopher Adam Smith that describes the incentives which free markets sometimes create for self-interested people to accidentally act in the public interest, even when this is not something they intended. Smith originally mentioned the term in two specific, but different, economic examples. It is used once in his Theory of Moral Sentiments when discussing a hypothetical example of wealth being concentrated in the hands of one person, who wastes his wealth, but thereby employs others. More famously, it is also used once in his Wealth of Nations, when arguing that governments do not normally need to force international traders to invest in their own home country. In both cases, Adam Smith speaks of an invisible hand, never of the invisible hand.
Going far beyond the original intent of Smith's metaphor, twentieth-century economists, especially Paul Samuelson, popularized the use of the term to refer to a more general and abstract conclusion that truly free markets are self-regulating systems that always tend to create economically optimal outcomes, which in turn cannot be improved upon by government intervention. The idea of trade and market exchange perfectly channelling self-interest toward socially desirable ends is a central justification for newer versions of the laissez-faire economic philosophy which lie behind neoclassical economics.
