In 1964, when race relations in America were under the sway of Martin Luther King's dream of future amity, and before President Johnson's war policy had destroyed the moral cohesion of the country, Paul C. Nagel published his impressive study, One and Indivisible: The Union in American Thought, 1776-1860. Now his second massively researched volume, This Sacred Trust: American Nationality, 1798-1898 (Oxford University Press; 376 pp.; $9.50), brings his account down, with some shift of emphasis, to the debates over imperialism occasioned by the War with Spain. Though the book ends almost seventy-five years ago, it has an obvious timeliness—not only because American imperialism is again a subject of worldwide debate but because American commitment to a sacred trust is seriously weakening. The traditional grounds of American loyalty are rapidly dissolving.