On the other hand, you must not think for a moment that what I present to you as the psychoanalytic conception is a purely speculative system. Indeed, it is a sum total of experiences and observations, either their direct expression or their elaboration. Whether this elaboration is done adequately and whether the method is justifiable will be tested in the further progress of the science. After two and a half decades, now that I am fairly advanced in years, I may say that it was particularly difficult, intensive and all-absorbing work which yielded these observations. I have often had the impression that our opponents were unwilling to take into consideration this objective origin of our statements, as if they thought it were only a question of subjective ideas arising haphazard, ideas to which another may oppose his every passing whim. This antagonistic behavior is not entirely comprehensible to me. Perhaps the physician's habit of steering clear of his neurotic patients and listening so very casually to what they have to say allows him to lose sight of the possibility of deriving anything valuable from his patients' communications, and therefore, of making penetrating observations on them. I take this opportunity of promising you that I shall carry on little controversy in the course of my lectures, least of all with individual controversialists. I have never been able to convince myself of the truth of the saying that controversy is the father of all things. I believe that it comes down to us from the Greek sophist philosophy and errs as does the latter through the overvaluation of dialectics. To me, on the contrary, it seems as if the so-called scientific criticism were on the whole unfruitful, quite apart from the fact that it is almost always carried on in a most personal spirit. For my part, up to a few years ago, I could even boast that I had entered into a regular scientific dispute with only one scholar (Lowenfeld, of Munich). The end of this was that we became friends and have remained friends to this day. But I did not repeat this attempt for a long time, because I was not certain that the outcome would be the same.