H.G. Callaway’s critical edition of William James's Essays in Radical Empiricism evaluates this classic work of American philosophy and the pragmatist tradition partly on the basis of the functional psychology of James's magnum opus, The Principles of Psychology. The edition also brings in later, Darwinian-functionalist, American psychology—which James did much to inspire—and contemporary developments in functional, cognitive psychology and neuroscience. James’s own text has been annotated throughout to render his references and theoretical concerns explicit and to briefly indicate points of criticism. The edition features an expanded bibliography that includes both historical and contemporary sources, as well as a new, comprehensive index. The chief arguments of the edition center on criticism of James's claims for "radical empiricism," his doctrine of "pure experience," and the doubtful role as evidence James attributed to stand-alone introspection and Jamesian “retrospection.” Enlisting results from the logic of relations, contemporary empiricism, historical and contemporary developments in cognitive psychology, and experimental neuroscience, Callaway argues for the importance of James on functional relations—to be interpreted in the manner of the scientific naturalism prominent in The Principles of Psychology. Too often, James’s late philosophical views have overshadowed the accomplishments of his earlier work in psychology. Overall, this new edition indicates the scientific virtues of functionalism in cognitive psychology and shows the relevance of James’s functional psychology to contemporary cognitive theory.