Almost three years passed since the Faculty of Economics of the University of Groningen celebrated its 25th Anniversary in 1973. Late, but not too late we hope, to present the lectures of most of our distinguished guests, who came from the United States and different European Countries to inform the Congress participants of their opinion and ideas on "25 Years of Economic Theory: Retrospect and Prospect. " The problems we met in publishing the lectures, in accordance with the agreement we made with our guests, are not unusual, as everyone knows who has been an editor of such a volume before. The promise to give a lecture and to write it down afterwards as well is much more difficult to maintain than only to give a speech. Everybody knows there is nothing so terrifying as to be reminded of your promise to write down your lecture, especially if only a type-written text, put down from a tape, is at your disposal. You are sure of your remembrance: "That very day I heard applause, there were friendly words and perhaps a state of not ending enthusiasm. And now I receive this type-written text of my speech with a request, full of innocence, of these friendly committee members, "will you be so kind as to prepare your text for publication ']" But this one, is this my text? Unbelievable.