This is a study of the foreign policy views of Arthur James Balfour (1848–1930), British Prime Minister and Foreign Secretary, which examines his understanding of foreign relations, his perception of contemporary foreign and Imperial affairs, and his prescriptions for British policy. The book spans international thought, diplomatic history, and biography. Theory is, however, not divorced from practice, still less practice from people. In elucidating Balfour's mind, the author touches on most of the major issues of four decades of international history and some fundamental questions of international relations. Little attention has been paid hitherto to Balfour's political thought, but here he is shown as an intellectual with a deep and coherent philosophy, which led him to emphasise the importance of Anglo-American partnership in world affairs.