If two objects or human beings show similar behaviour in all their relevant aspects open to observation, the assumption of some unobservable hidden d… - John Harsanyi

In November 1944 the Nazi authorities finally decided to deport my labor unit from Budapest to an Austrian concentration camp, where most of my comrades eventually perished. But I was lucky enough to make my escape from the railway station in Budapest, just before our train left for Austria. Then a Jesuit father I had known gave me refuge in the cellar of their monastery.

Following von Neumann and Morgenstern [7, p. 30], we distinguish between games with complete information, to be sometimes briefly called C-games in this paper, and games with incomplete information, to be called I-games. The latter differ from the former in the fact that some or all of the players lack full information about the "rules" of the game, or equivalently about its normal form (or about its extensive form). For example, they may lack full information about other players' or even their own payoff functions, about the physical facilities and strategies available to other players or even to themselves, about the amount of information the other players have about various aspects of the game situation, etc. In our own view it has been a major analytical deficiency of existing game theory that it has been almost completely restricted to C-games, in spite of the fact that in many real-life economic, political, military, and other social situations the participants often lack full information about some important aspects of the "game" they are playing.

Early in 1954 I was appointed Lecturer in Economics at the University of Queensland in Brisbane. Then, in 1956, I was awarded a Rockefeller Fellowship, enabling me and Anne to spend two years at Stanford University, where I got a Ph.D. in economics, whereas Anne got an M.A. in psychology. I had the good fortune of having Ken Arrow as advisor and as dissertation supervisor. I benefitted very much from discussing many finer points of economic theory with him. But I also benefitted substantially by following his advice to spend a sizable part of my Stanford time studying mathematics and statistics. These studies proved very useful in my later work in game theory.