This book concerns two extraordinary men who shaped twentieth-century philosophy: William James (1842–1910) and Ludwig Wittgenstein (1889–1951). James is the author of the thousand-page masterpiece, The Principles of Psychology (1890), a rich blend of philosophy, psychology, and personal reflection that has given us such ideas as “the stream of thought,” and the baby's impression of the world “as one great blooming, buzzing confusion” (PP, 462). Ranging from the functions of the brain to multiple personalities, from intellect to will, to our general sense of reality, James's Principles is more than the first great psychology text. It contains seeds of pragmatism and phenomenology, and influenced thinkers as diverse as Edmund Husserl, Bertrand Russell, and John Dewey. It is, as Jacques Barzun has written, “an American masterpiece which, quite like Moby Dick, ought to be read from beginning to end at least once by every person professing to be educated.”

James's pioneering survey of religious psychology, The Varieties of Religious Experience (1902), introduced such terms as “the divided self” and “the sick soul,” and an account of religion's significance in terms of its “fruits for life.” James's religious concerns are also evident in The Will to Believe and Other Essays in Popular Philosophy (1897), Human Immortality: Two Supposed Objections to the Doctrine (1898), and A Pluralistic Universe (1909). James oscillated between thinking that a “study in human nature” such as Varieties could contribute to a “Science of Religion” and the belief that religious experience involved an altogether supernatural domain, somehow inaccessible to science but accessible to the individual human subject.