Essays in Radical Empiricism is a collection of Williams James essays edited and published posthumously by James' colleague and biographer Ralph Barton Perry. It was assembled from a collection of reprinted journal articles published which James had deposited at the Harvard University Library and the Harvard Department of Philosophy for supplemental use by his students. William James was a pioneering American psychologist and philosopher trained as a medical doctor. He wrote influential books on psychology, educational psychology, psychology of religious experience and mysticism, and the philosophy of pragmatism. He gained widespread recognition with his monumental Principles of Psychology, totaling twelve hundred pages in two volumes, which took twelve years to complete.