Mercantilism
The doctrine that national wealth is a fixed hoard to be captured from rivals, which built Europe's empires and justified their trade monopolies.
Mercantilism is the belief that a country grows rich by selling more than it buys and accumulating the difference in gold and silver, and that since the world's stock of treasure is finite, one nation's gain must be another's loss. No one wrote it down as a system while it was operating. The name came from its most famous critic: Adam Smith attacked what he called the mercantile system in 1776, and the label stuck to two and a half centuries of policy that had been made piecemeal by kings who needed money and merchants who wanted protection.
What it told governments to do
The prescriptions follow from the premise. Export finished goods, import raw materials, and tax or ban the reverse. Protect domestic manufactures behind tariffs. Subsidize industries that earn foreign silver, especially textiles. Build a merchant marine, because carrying your own trade keeps the freight charges at home, and a merchant marine doubles as a naval reserve in wartime. Keep wages low so exports stay cheap. And acquire colonies, which are valuable in exactly two ways: as sources of raw materials you would otherwise buy from a rival, and as captive markets that must buy from you.
England's Navigation Acts, beginning in 1651, are the doctrine in statute. Goods coming to England had to travel in English ships or ships of the producing country, colonial products such as sugar and tobacco had to be shipped to England first even when the buyer was elsewhere, and the colonies were forbidden manufactures that would compete with the home industry. Jean-Baptiste Colbert, running French finances for Louis XIV from 1665, did the same work with state-chartered monopolies, royal manufactories, canal building, and tariff walls, plus chartered companies to run the colonial trade.
Why states liked it
Mercantilism survived because it answered the real problem of early modern rulers, which was not aggregate prosperity but solvency in wartime. Bullion paid for mercenaries and fleets. A state with silver in the treasury and shipwrights in its ports could fight; a state with a rich but unarmed merchant class could be conquered by one. Seen this way, mercantilism was less an economic theory than a national security policy that treated commerce as a branch of war, which is why the era's trade disputes turned into shooting wars with such regularity.
The costs landed on people with no vote in the matter. Colonial economies were deliberately shaped as suppliers and forbidden to develop. The plantation systems of the Caribbean and Brazil, and the Atlantic slave trade that supplied them, were mercantilist enterprises: closed circuits designed so that value accumulated in the metropole. American colonists who resented being told what they could manufacture and whom they could sell to were resenting the Navigation Acts, and the revolution that followed was in part a fight about the system.
The critique, and the return
Adam Smith's argument in The Wealth of Nations was that the premise was simply wrong. Wealth is not the stock of metal in a vault, it is the flow of goods and services a country can produce and consume, and trade is not zero-sum, because both sides gain from exchanging what they make cheaply for what they do not. David Ricardo formalized this into comparative advantage in 1817. Britain, having built an empire on mercantilist rules, repealed the Corn Laws in 1846 and became the champion of free trade, which is what dominant producers usually become.
The doctrine never really died. Every state that has industrialized quickly, from Germany and the United States in the nineteenth century to Japan, South Korea, and China in the twentieth, did it behind tariffs, subsidized champions, and managed currencies. The modern vocabulary has changed to trade deficits, industrial policy, supply chain security, and export controls, but the intuition underneath is the old one: that trade is a contest, that surpluses are victories, and that depending on a rival for something essential is a form of weakness. Economists have been calling that a fallacy for 250 years, and governments keep acting on it anyway, because for a state worried about war rather than welfare it has never been entirely wrong.