A profoundly influential figure in American psychology, William James (1842–1910) was also a philosopher of note who adopted Charles S. Peirce's theories as a basis for his own conception of pragmatism. For James, this meant an emphasis on "radical empiricism" and the concept that the meaning of any idea — philosophical, political, social, or otherwise — has validity only in terms of its experiential and practical consequences. In this book, James tests competing systems of thought in the "marketplace of actual experience" to determine their validity. In other words, he examines whether adopting a particular philosophical theory or way of looking at the world makes an actual difference in individual conduct. James not only makes a strong case for his own ideas but also mounts a powerful attack against the transcendental and rationalist tradition.