… is from page 130 of volume III (“The Political Order of a Free People,” 1979) of Hayek’s Law, Legislation, and Liberty (subheading deleted):
We shall have to reconcile ourselves to the still strange fact that in a society of free men the highest authority must in normal times have no power of positive commands whatever. Its sole power should be that of prohibition according to rule, so that it would owe its supreme position to its commitment with every act to a general principle.
The fundamental reason why the best that a government can give a great society of free men is negative is the unalterable ignorance of any single mind, or any organization that can direct human action, of the immeasurable multitude of particular facts which must determine the order of its activities. Only fools believe they know all, but there are many fools.
Hayek here spells out his chief reason – the limits of human knowledge – for why policy-making should be guided in a principled way by general abstract rules rather than pragmatically by discretion aimed at addressing each and every particular situation that reveals itself to policy-makers’ attention. The case for rules over discretion is strengthened when we add to Hayek’s reason the further reality that policy-makers’ attention is inevitably distorted by political considerations (such as those identified by public-choice scholarship) and by the psychological quirks identified by behavioral psychologists.
