They devised a new economic policy to ensure the profitability of the colonies as Europeans expanded their market reach into the colonial sphere. European perceptions of wealth from the 1500s to the late 1700s were shaped by the philosophy of mercantilism. Mercantilism held that there was only a limited amount of wealth in the world, as measured in gold and silver bullions. Nations had to amass wealth in order to gain power by mining these precious raw materials from their colonial possessions. Mercantilists did not believe in free trade, arguing instead that to create wealth and improve state power, the nation should control trade. Colonies existed to strengthen the colonizing nation in this view.