The author, professor of political science at Johns Hopkins, is a philosopher of international relations. This study, like all his work, provides no instant enlightenment, but will repay those who have the time and stamina to wrestle with close reasoning, complex syntax, and a high level of abstraction. To oversimplify: his argument is that the U.S. historically has avoided the choice of control through empire or through balance-of-power politics while periodically seeking a non-existent third stance - separation.