Now you will surely judge that so to reject the discussion of literature must evidence stubborness, a very special obtuseness against objections, or, as the kindly colloquialisms of science have it, "a complete personal bias." In answer, I would say that should you attain to a conviction by such hard labor, you would thereby derive a certain right to sustain it with some tenacity. Furthermore, I should like to emphasize the fact that I have modified my views on certain important points in the course of my researches, changed them and replaced them by new ones, and that I naturally made a public statement of that fact each time. What has been the result of this frankness? Some paid no attention at all to my self-corrections and even to-day criticize me for assertions which have long since ceased to have the same meaning for me. Others reproach me for just this deviation, and on account of it declare me unreliable. For is anyone who has changed his opinions several times still trustworthy; is not his latest assertion, as well, open to error? At the same time he who holds unswervingly to what he has once said, or cannot be made to give it up quickly enough, is called stubborn and biased. In the face of these contradictory criticisms, what else can one do but be himself and act according to his own dictates? That is what I have decided to do, and I will not allow myself to be restrained from modifying and adapting my theories as the progress of my experience demands. In the basic ideas I have hitherto found nothing to change, and I hope that such will continue to be the case.