Many disciplines create books of readings by the dozens; it is a rare event when a reader helps to create a discipline. On its publication in 1952, Main Currents of Western Thought did just that. "As of the moment, intellectual history is both popular and suspect," Franklin Le Van Baumer wrote in his introduction, adding that it "currently enjoys something like a vogue on both sides of the Atlantic." This same introduction, entitled "Methodology and Interpretation," went far toward transforming a vogue into a respectable field of study by defining its goals and its methods, its problems and its pitfalls.  In the quarter of a century since its first appearance, Main Currents has remained unquestionably the leading reader in its field. The illuminating short essays that introduce sections and subsections are well known, but the continuing usefulness of any reader depends upon the quality of its selections. Baumer has sought out passages that best represent and illuminate the ideas and preoccupations of each age. He has found them in the works of the great, including Augustine, Aquinas, Dante, Luther, Newton, Voltaire, Darwin, Whitehead, and Freud. But he has also discovered telling statements in writings less widely known: Ramón Lull on chivalry (13th century), Henry Peacham on "the complete gentleman" and Leonard Busher on religious liberty (both 17th century), Louis-René de la Chalotais on education (18th century), Samuel Smiles on "self-help" (19th century) and Virgil Gheorgiu on mechanization (20th century).  Each of the previous editions of Main Currents has contained considerable new material. For this edition, the fourth, Baumer has rewritten the introductory essay to the section on "the age of anxiety" and the bibliographical note, and he has added thirteen new excerpts. Their authors range from Luther and Pascal to Bultmann, Bonhoeffer, and Heisenberg, enriching the earlier sections of the book and introducing three major figures of the 20th century.