William James lived at the boundaries and did his best work there. In 1890, James published his magnum opus, The Principles of Psychology, a foundational work in which he makes clear distinctions about the kinds of assumptions each discipline takes for granted and then subjects these assumptions to critical examination. For many years, this was a widely used text that uniquely blended his personal reflections with his ideas on physiology, philosophy, and psychology. Throughout the book and his career, James extravagantly crossed the boundaries of multiple disciplines. This volume is comprised of a series of in-depth interviews with ten North American scholars and clinical practitioners who have similarly spent their lengthy careers working at the interdisciplinary edges of mainstream psychological discourse.