The slippery role of information as an economic good is of deep significance to economic behavior, especially in the relatively information-rich mode… - Kenneth Arrow

The uncertainty of the future is inescapable, one must think about it and arrive at plans for action. A statement attributed to a number of thinkers is, "Prediction is very difficult, especially of the future." Postdiction, knowing what went on in the past, is also difficult. The past, however, is our basis for understanding the future.

If the state of information (the set of signals received) is given and constant, then optimal choice is a problem of decision making under a given uncertainty, a situation that has been the subject of considerable analysis in the last thirty years. The problems of the economics of information proper arise when the probability distribution of states of the world is a variable. In the language adopted here, the signals received can vary. The existence of signals creates two important possibilities for the improvement of decision making. The first is taking advantage of the existence of signals. If the individual knows that a signal will be received before the decision has to be made, his optimal choice should be a function of the signal. We can think, alternatively but equivalently, of making the decision after the receipt of the signal and basing it on the probability distributions of consequences conditional on the signal, or of making the decision in advance for all possible values of the signal.

While economic theory in general may be defined as the theory of how an economic condition or an economic development is determined within an institutional framework, the deals with how to judge whether one condition can be said to be better in some way than another and whether it is possible, by altering the institutional framework, to achieve a better condition than the present one.