It is doubtful whether I shall be able to meet the high standards set by previous speakers. I shall not prove deep theorems. I shall not present astonishing new results. Instead, I shall try to catch your attention with a fictitious dialogue. I shall employ the help of imaginary discussants like the “Bayesian” or the “experimentalist.” A “chairman” will determine who speaks next, but he shall also make his own remarks.

Chairman: I open the discussion with a question: What do we know about the structure of human economic behavior?

The Bayesian has signaled his willingness to answer this question. I give the floor to the Bayesian.

Bayesian: As far as economic activities are concerned, it is justified to assume that man is a rational being. Since Savage (1954) simultaneously axiomatized utility and subjective probability, we know what rational economic behavior is. It is the maximization of subjectively expected utility.

Chairman: Among us is an economist. I would like to ask him if this is the agreed upon opinion in economic theory.

Economist: Yes, to a large extent, this is the agreed upon opinion. Most of microeconomics takes Bayesianism for granted. However, there are exceptions. Some theorists have different views.