THE PRINCIPLES OF PSYCHOLOGY BY WILLIAM JAMES PROFESSOR OF PSYCHOLOGY IN HARVARD UNIVERSITY IN TWO VOLUMES VOL. I NEW YORK HENRY HOLT AND COMPANY 1918 TO MY DEAR FRIEND FRANÇOIS PILLON. AS A TOKEN OF AFFECTION, AND AN ACKNOWLEDGMENT OF WHAT I OWE TO THE CRITIQUE PHILOSOPHIQUE. PREFACE. The treatise which follows has in the main grown up in connection with the author's class-room instruction in Psychology, although it is true that some of the chapters are more 'metaphysical,' and others fuller of detail, than is suitable for students who are going over the subject for the first time. The consequence of this is that, in spite of the exclusion of the important subjects of pleasure and pain, and moral and æsthetic feelings and judgments, the work has grown to a length which no one can regret more than the writer himself. The man must indeed be sanguine who, in this crowded age, can hope to have many readers for fourteen hundred continuous pages from his pen. But _wer Vieles bringt wird Manchem etwas bringen_; and, by judiciously skipping according to their several needs, I am sure that many sorts of readers, even those who are just beginning the study of the subject, will find my book of use. Since the beginners are most in need of guidance, I suggest for their behoof that they omit altogether on a first reading chapters 6, 7, 8, 10 (from page 330 to page 371), 12, 13, 15, 17, 20, 21, and 28. The better to awaken the neophyte's interest, it is possible that the wise order would be to pass directly from chapter 4 to chapters 23, 24, 25, and 26, and thence to return to the first volume again. Chapter 20, on Space-perception, is a terrible thing, which, unless written with all that detail, could not be fairly treated at all. An abridgment of it, called 'The Spatial Quale,' which appeared in the Journal of Speculative Philosophy, vol. xiii, p. 64, may be found by some persons a useful substitute for the entire chapter.