Hayek on Rules, Tradition, and Freedom

There is advantage in obedience to such [moral and other social] rules not being coerced, not only because coercion as such is bad, but because it is, in fact, often desirable that rules would be observed only in most instances and that the individual should be able to transgress them when it seems to him worthwhile to incur the odium which this will cause. It is also important that the strength of the social pressure and of the force of habit which insures their observance is variable. It is this flexibility of voluntary rules which in the field of morals makes gradual evolution and spontaneous growth possible, which allows further experience to lead to modifications and improvements. Such an evolution is possible only with rules which are neither coercive nor deliberately imposed -- rules which, though observing them is regarded as merit and though they will be observed by the majority, can be broken by individuals who feel that they have strong enough reasons to brave the censure of their fellows. Unlike any deliberately imposed coercive rules, which can be change only discontinuously and for all at the same time, rules of this kind allow for gradual and experimental change. The existence of individuals and groups simultaneously observing partially different rules provides the opportunity for the selection of the more effective ones. 

F. A. Hayek, The Constitution of Liberty (1960: 62-63)