If we accept values as given and consistent, if we postulate an objective description of the world as it really is, and if we assume that the decision maker's computational powers are unlimited, then two important consequences follow. First, we do not need to distinguish between the real world and the decision maker's perception of it: he or she perceives the world as it really is. Second, we can predict the choices that will be made by a rational decision maker entirely from our knowledge of the real world and without a knowledge of the decision maker's perceptions or modes of calculation. (We do, of course, have to know his or her utility function.)

H.A. Simon (1986), "Rationality in psychology and economics," Journal of Business, p. 210-11”