The national interest, often referred to by the French expression raison d'État ("reason of State"), is a country's goals and ambitions whether economic, military, or cultural. The concept is an important one in international relations where pursuit of the national interest is the foundation of the realist school.
In early human history the national interest was usually viewed as secondary to that of religion or morality. To engage in a war rulers needed to justify the action in these contexts. The first thinker to advocate for the primacy of the national interest is usually considered to be Niccolò Machiavelli.
The practice is first seen as being employed by France under the direction of its Chief Minister Cardinal Richelieu in the Thirty Years' War when it intervened on the Protestant side, despite its own Catholicism, to block the increasing power of the Catholic Holy Roman Emperor. At Richelieu's prompting, Jean de Silhon defended the concept of reason of state as "a mean between what conscience permits and affairs require." The notion of the national interest soon came to dominate European politics that became fiercely competitive over the next centuries. It is a form of reason "born of the calculation and the ruse of men" and makes of the state "a knowing machine, a work of reason"; the state ceases to be derived from the divine order and is henceforth subject to its own particular necessities (E. Thuau, 1966).
States could now openly embark on wars purely out of self-interest. Mercantilism can be seen as the economic justification of the aggressive pursuit of the national interest.