Intellectuals analyze the operations of international systems; statesmen build them. And there is a vast difference between the perspective of an analyst and that of a statesman. The analyst can choose which problem he wishes to study, whereas the statesman’s problems are imposed on him. The analyst can allot whatever time is necessary to come to a clear conclusion; the overwhelming challenge to the statesman is the pressure of time. The analyst runs no risk. If his conclusions prove wrong, he can write another treatise. The statesman is permitted only one guess; his mistakes are irretrievable. The analyst has available to him all the facts, he will be judged on his intellectual power. The statesman must act on assessments that cannot be proved at the time that he is making them; he will be judged by history on the basis of how wisely he managed the inevitable change and, above all, by how well he preserves the peace.
Henry Kissinger, Diplomacy (Simon and Schuster, 1994) p.27