To Leo Wolman and Wesley Clair lviitchell, my colleagues at the New School for Social Research, I am indebted for much valuable criticism and suggestion; to Miss Lurene macdonald, the Librarian at the School, for assistance in the classification of the material and preparing the index; to my ever-helpful sister, Ida Kallen, and to my old friend and pupil, Mar vin Lowenthal, for aid in reading the manuscript and getting it ready for the press; to my dear fellow-worker, Julian W. Mack, for help with the proof and many valuable suggestions and corrections. These acknowl edgments can only scantily express What I owe them.