THE separate chapters of this book have already been published as essays in periodicals. The first, second, third, and seventh appeared in The Hibbert Journal; the fourth, in The Philosophical Magazine and in the University of Cincin-nati Studies; the fifth, in The Monist; and the sixth, in The Unpopular Review. But they have been rewritten and en-larged so as to form chapters for a connected discussion of the Limitations of Science. This was not a difficult task since I have had this purpose in mind from the beginning.