Mercantilism is defined for this discussion as a policy of government that expressed in the economic sphere the spirit of nationalism that animated the growth of the national state in early modern times. The policy aimed to gain for the nation a high degree of security or self-sufficiency, especially as regards food supply, raw materials needed for essential industries, and the sinews of war. This end was to be achieved in large measure by means of an effective control over the external activities and resources upon which the nation was dependent. In turn, that urge impelled the mercantilists to prefer colonial dependencies to independent foreign countries in seeking sources of supply. If the state could not free itself completely from trade with foreign nations, it sought to control that trade in its own interest as much as possible. To realize such objectives, mercantilism embraced three subordinate and related policies. The Corn Laws fostered the nation's agriculture and aimed to realize the ideal of self-sufficiency as regards food supply. State aids to manufacturing industries, such as the protective tariff, sought to provide essential finished goods, including the sinews of war. The Navigation Acts were intended to assure that foreign trade would be carried on in such a way as to yield the maximum advantage to the state concerned.