原文 (英語)

PREFACE The substance of these chapters was delivered as a course of lectures at Harvard University, Dartmouth and Wellesley Colleges, Western Reserve University, the University of California, and the Twentieth Century Club of Boston. A part of the sixth chapter was used as an address before the Phi Beta Kappa Society of Harvard, and another part before the Philosophical Union of Berkeley, California. Several of these audiences have materially aided my work by their searching criticism