A state's foreign policy is constrained by parameters that inhere in the structure of the international system and in the nation's own political‐constitutional, social, and economic systems. The latter, domestic parameters, include “public opinion.” Because the public is largely ignorant of foreign affairs, policy‐making elites have wide scope for acting more rationally than would otherwise be possible, although public opinion operates on the second‐order effects of foreign policy (e.g., taxes, casualties)—inviting mismatches of objectives and means. The prevalent nonrational theories of (...) foreign‐policy derivation are themselves largely ignorant of the dominantly rational processes of the state, particularly in its foreign and military functions. (shrink)