Professor Royce divides modern philosophy into three great periods, of which the first was one of pure and simple naturalism. The supernatural had then only a secondary interest, and thought was governed by three ideas—“that nature is a mechanism, that human reason is competent to grasp the truth of nature, and that, since nature’s truth is essentially mathematical, geometry is the model science, whose precision and necessity philosophy, too, must imitate.” During the second period of modern philosophy there was a gradual change of thought objectivity. Reason was still the instrument, but it was employed on the mind itself. It came to be recognised that if man is part of nature’s mechanism, he is a knowing mechanism. The age was, however, more than one of self-analysis. Rousseau introduced a sentimental tendency from which came “a revival of passion, of poetry, and of enthusiasm, whose influence we shall never outgrow.” To it is traceable the French Revolution which overthrew all the mechanical restraints of civilisation, and “demonstrated afresh to the world’s outer sense the central importance of passion in the whole life of humanity.” The period of modern philosophy, which still continues, began with the publication of Kant’s “Critique of Pure Reason,” the essential doctrine of which is that man’s nature is the real creator of man’s world, that visible nature is the expression of the human spirit, the inner structure of which is therefore the deepest truth for us. This idea is “as old as deeper spiritual faith itself,” and yet it is the very soul of all our modern life because it is “the essentially humane view of reality.” For fifty years Kant’s ideas ruled philosophic thought, and then, through the progress of science, the doctrine of evolution received formulation, and confirmation and “external nature has once more gained for us an imposing authority which makes us in many ways sympathise afresh with the pure naturalism of the seventeenth century.” We are compelled to omit any account of the author’s study of the philosophies of Spinoza, Locke, and Berkeley, or the philosophic systems of Kant and his successors of the German School of Idealists. Nor can we say anything as to the doctrine of Evolution, which Professor Royce rightly regards as having had its rise long before Darwin or Herbert Spencer. Before proceeding to state his own views, the author takes a cursory glance at modern empirical monism which he affirms to be rather a suggestion than a philosophy. It is not surprising, therefore, that he is not content with it although he makes use of its ideas.