Allow me to preface my remarks today by saying that I am not going to give a lecture in the usual sense of communicating results or presenting a systematic statement. Rather, what I have to say will remain on the level of an essay; it is no more than an attempt to take up and further develop the problems of the so-called Frankfurt discussion. I recognize that many uncomplimentary things have been said about this discussion, but I am equally aware (...) that it approaches the problem correctly and that it would be wrong always to begin again at the beginning. (shrink)