The thread connecting the following essays is already indicated on the title-page. They all illustrate, each from the field of its own subject, the metaphysical theory which I venture to call Personal Idealism. Partly, they show how this theory draws its arguments, as if unexpectedly, from the discussion now of this topic taken up for its own philosophical interest, and now of that; partly, they in turn reflect the light of the theory upon the discussion of the topic. To the running reader, the several papers, with titles so widely divergent, would hardly suggest any common trend of thought. They all have it, however; in fact, taken together, they may be said to present the mentioned philosophic theory in its bearings on all the chief human concerns, — on knowledge, joy, and devotion; on Science, Art, and Religion. Still, in view of the great diversity of their subjects, one might easily fail of a clear and firm seizure of the thought that unites them, unless the clue were given by some words of introduction.