We are told by Professor Royce in the preface to this book, that we are indebted for it to the lady friend to whom it is gracefully dedicated, who asked him “for some account of the more significant spiritual possessions of a few prominent modern thinkers,” to be related “in comparatively brief and untechnical fashion.” The larger portion of the work is taken up with that subject, exhibiting the general growth of modern philosophical thought beginning with Spinozism, and terminating with Monism as the outcome of the doctrine of Evolution. The author’s purpose is constructive, however, as well as expository. He has his own philosophical creed, suggested by what he knows of the progress and outcome of modern thought, and the second portion of the work is the expression of his thoughts on the world-conception which he regards as embodying the true spirit of modern philosophy. Professor Royce justly lays stress on the fact that the theory of evolution is the product of a genuine and continuous growth. He dwells particularly, moreover, on the distinction between the _epistemological_ sense of idealism, which “involves a theory of the nature of our human knowledge,” and its _metaphysical_ sense, in which it is “a theory as to the nature of the real world, however we may come to know that nature.” It is in accord with the latter sense that Fichte, Schelling, Hegel, and their allies, as believing matter to be an expression of the world-spirit, are referred to as the idealistic school; and it is in the metaphysical and not the epistemological sense that the term idealism has been used since Hegel. The opposite of a metaphysical idealist is “one who maintains the ultimate existence of wholly unspiritual realities at the basis of experience and as the genuine truth of the world—such unspiritual realities for instance as an absolute ‘Unknowable,’ or, again, as what Hobbes meant by ‘Body.’” This is not, however, the view of the author, who thinks that the metaphysical idealist alone is in possession of a successful solution for the epistemological problem.