It is a great pleasure to acknowledge the aid of my wife, whose interest and skill have been of special ser vice in the revision of the translations. Iam also in debted to my friends and former colleagues, Professor George M. Duncan, of Yale University, for the use of his list of the English translations of Kant's writings, which he has brought down to date for this volume, and Presi dent G. Stanley Hall, of Clark University, for access to special monographs in his private library.