I am old-fashioned enough to retain David Hume’s view that one can never derive “ought” propositions from “is” propositions. The two issues, method a… - Kenneth Arrow

Certainly, there is no general principle that prevents the creation of an economic theory based on other hypotheses than that of rationality.

Information, one of the fundamental determinants of production, laps over from one firm to another, yet the firm has so far seemed reasonably sharply defined in terms of legal ownership. It seems to me there must be increasing tensions between legal relations and fundamental economic determinants. Small symptoms are already appearing in the legal and economic spheres. There is continual difficulty in defining intellectual property. The United States courts, at least, have come up with some strange definitions of property.

The tension between chaotic behavior and perfect foresight was observed. Start with an equilibrium dynamics of a standard type derived from the hypothesis that future prices are predicted perfectly. Suppose that the solution to the difference equations characterizing the solution exhibits chaotic behavior. Is it realistic to assume that the future, even though deterministic, is in fact predictable? Clearly, part of the lessons drawn by natural scientists, especially meteorologists, from nonlinear dynamics is precisely the opposite; chaotic behavior implies that small errors of observation in the starting position may lead to virtually total unpredictability after some period of time. This creates no difficulties of consistency when the predictor is not part of the system being predicted. But when the predictors are the economic agents being examined, there is a fundamental inconsistency. This epistemological antinomy is reinforced by the empirical observation that actual behavior of prices of assets such as securities could never reasonably have been predicted; if it had, there would have been much more buying or selling at earlier stages.