Realism (international relations)

Realism in foreign policy is a doctrine that assumes that it may be entirely possible to work with otherwise hostile states when matters of common concern are involved, but one of the constraints is that the internal politics of a nation is not a matter of common concern and out of scope for the proposed cooperation. While Henry Kissinger is its most visible advocate, he was by no means the originator.

Hans Morgenthau, indeed, may have articulated it more clearly.

Kissinger had addressed the basic ideas going back to his senior thesis, which eventually became the book, A World Restored, which explored "balance of power" explanations for stability in early 19th century Europe. In the Nixon Administration, his first priority was replacing the containment policy against the Soviet Union and Chinea with détente, or a "lessening of tensions". Detente tends to specific to key issues, where realism has broader scope. It was a change from the containment policy, which expected to restrain and indeed weaken opposing power blocs through economic and psychological warfare. Detente, or the "lessening of tensions", assumed that the opponent could not be significantly weakened, but also accepted they would cooperate on mmaggers of common concern. It is a subset of realism (foreign policy), which further recognizes that states can have reason to cooperate on external policies, but it often would be impractical to change their internal practices.