Comparative study of the Muqaddimah of Ibn Khaldun and Thucydides' History of the Peloponnesian War reveals striking similarities not only in the methods and assumptions of the two historical thinkers, but also in the conclusions to which each was driven by his experience of history. Both men are naturalists, both empircists, both exponents of a critical approach to historiography. Yet neither is a reductionist. Both seek a lesson in history, and and both believe that the message of history is to be discovered in the careful study of historical laws revealed in the play of forces which are the expression of man's political and social nature. But beyond similarities of approach, there is a deep congruity of thought between the two authors, for both believe themselves to have glimpsed the pattern, learned the lesson of history. Both Ibn Khaldun and Thucydides have been led by their study of history to a cyclical, rather than linear view of historical process; both have been led, in developing their concepts of human and political reality, to a qualified relativism, which affords them, as I endeavor to show, a cautious but by no means pessimistic historical theodicy.