THIS second impression is, except for the corrections of minor mistakes and small additions to the bibliography, an exact reprint of the first edition. This does not imply that there is nothing in the book which I think should be altered; in fact, it implies exactly the opposite. Now I should not dare to write such a book at all. The capacity to make broad generalizations, to concentrate a number of ideas into a small compass in the hope that they will convey more of truth than of falsehood, is the result either of the rashness of youth or the wisdom of age. In the intervening period caution takes control, and if I were now to attempt a revision of this book, I should want to qualify every sentence with so many dependent clauses and parentheses that the book would lose whatever utility it has, which is, I hope, to provide an introduction to the subject which may stimulate the reader to pursue it further.
THE arguments stated in the preface to the second impression still apply, and I have made no attempt to revise the text of this book systematically. I have corrected a few mistakes which had survived into the second edition and have removed a few references to out-of-date literature. The Bibliography has, however, been completely revised and extended to include the large number of new and often well annotated editions of texts which have appeared in the last ten or fifteen years.