Harsanyi may be viewed as the last representative of the old welfare economics, to which he made a major contribution in the form of two arguments. The first one is often called the “impartial observer argument”. An impartial observer should decide for society as if she had an equal chance of becoming anyone in the considered population. This is a risky situation in which the standard decision criterion is expected utility. The computation of expected utility, in this equal probability case, yie