Circumstances have thus been such as to bring me in contact, sometimes fleeting and sometimes prolonged, with men who represent divers standpoints in psychopathology. Many of these have kindly placed their minds and their facilities at my disposal, and I hereby return thanks for the generosity and patience with which they treated an inquiring, if somewhat innocent, investigator. No one who knows the lay of the land in modern psychology, deeply pitted by the trenches and shell-holes of battling schools, will imagine that all the men whom I am to name see eye to eye with one another, or that they will look with equanimity upon the results of my explorations. To name them is, I hope, not unduly to incriminate them. Among those from whom assistance has been received are to be included: Dr. William Healy, Judge Baker Foundation, Boston; Dr. William A. White, superintendent of St. Elizabeth’s Hospital, Washington, D.C.; Dr. Ross Chapman, superintendent of Sheppard and Enoch Pratt Hospital, Towson, Maryland; Dr. Earl D. Bond, superintendent of the Pennsylvania State Hospital, Philadelphia; Dr. Mortimer Raynor, superintendent of Bloomingdale Hospital, White Plains, New York; Dr. C. MacFie Campbell, superintendent of the Boston Psychopathic Hospital, Boston; Dr. Harry Stack Sullivan, formerly of Sheppard and Enoch Pratt Hospital; Dr. N. D. C. Lewis, St. Elizabeth’s Hospital; Dr. Samuel W. Hamilton, Bloomingdale Hospital; Dr. Gregory Zilboorg, Bloomingdale Hospital; Dr. F. L. Wells, Boston Psychopathic Hospital; Dr. Edouard Hitschmann, Vienna; Dr. Paul Federn, Vienna; Dr. Alfred Adler, Vienna; Dr. Wilhelm Stekel, Vienna; Dr. S. Ferenczi, Budapest; Dr. Theodor Reik, Berlin; Dr. Franz Alexander, Berlin (now of the University of Chicago). My colleagues, Dr. Stewart B. Sniffen and Professor Leonard D. White, made valuable suggestions during the process of editing the manuscript, several of which I adopted. Permission to quote freely from my previous publications was received from the editors of the _American Political Science Review, American Journal of Psychiatry, Journal of Abnormal and Social Psychology, International Journal of Ethics_, and from the University of Chicago Press and the Chicago Association for Child Study and Parent Education. I wish especially to express my gratitude to those who cannot be singled out by name, but whose co-operation in submitting themselves to prolonged scrutiny was of the greatest possible help. It ought to be pointed out that the cases actually cited are only a fraction of those which I have examined, or which I have in my possession. Only enough cases have been abstracted to serve the purposes of exposition, to supply a background for the theoretical material. The obscurities which result from an unlimited multiplication of “little Willie stories” have been sought to be avoided by curtailing their number and their extent.