On the other hand, you are not for a moment to suppose that the psycho-analytic point of view which I shall lay before you is a speculative system of ideas. On the contrary, it is the result of experience, being founded either on direct observations or on conclusions drawn from observation. Whether these have been drawn in an adequate or a justifiable manner future advances in science will show; after nearly two and a half decades and now that I am fairly well advanced in years I may say, without boasting, that it was particularly difficult, intense, and all-absorbing work that yielded these observations. I have often had the impression that our opponents were unwilling to consider this source of our statements, as if they looked upon them as ideas derived subjectively which anyone could dispute at his own sweet will. This attitude on the part of my opponents is not quite comprehensible to me. Perhaps it comes from the circumstance that physicians pay so little attention to neurotics and listen so carelessly to what they say that it has become impossible for them to perceive anything in the patients’ communications or to make detailed observations from them. I will take this opportunity of assuring you that in these lectures I shall make few controversial references, least of all to individuals. I have never been able to convince myself of the truth of the saying that “strife is the father of all things.” I think the source of it was the philosophy of the Greek sophists and that it errs, as does the latter, through the over estimation of dialectics. It seems to me, on the contrary, that scientific controversy, so-called, is on the whole quite unfruitful, apart from the fact that it is almost always conducted in a highly personal manner. Until a few years ago I could boast that I had only once been engaged in a regular scientific dispute, and that with one single investigator, Löwenfeld of Munich. The end of it was that we became friends and have remained so to this day. But I did not repeat the experiment for a very long time because I was not certain that the outcome would be the same.