Preface to the Revised Edition, 1918

Thus it seems to me that, on the one hand, this book occupies a position completely independent of my writings on actual spiritual scientific matters, and yet, on the other hand, it is also most intimately connected with them. All this has caused me now, after twenty-five years, to republish the content of this book practically unaltered in all essentials. I have, however, made additions of some length to several chapters. The misunderstandings of my argument which have come to my attention seemed to make these detailed extensions necessary. Alterations have been made only where what I said a quarter of a century ago appeared to me clumsily expressed. (Only ill-will could find in these changes occasion to suggest that I have changed my fundamental conviction.)