PREFACE TO THE SECOND EDITION
IN this new edition of my book I have made no essential changes, but here and there the argument has been strengthened by the addition of facts which have come to my knowledge since the appearance of the first edition. The most important of these new facts will be found in the second chapter.
I take this opportunity of expressing my warm appreciation of the thorough way in which the ideas set forth in this book have been discussed by many critics in England and elsewhere. Translations of the work have appeared, or are about to appear, in German, Swedish, French, Italian, and Russian.