Weber, Law and Sociology

"for sociological purposes there does not exist, as there does for the law, a rigid alternative between the validity and lack of validity of a given order. On the contrary, there is a gradual transition between the two extremes, and also it is possible, as it has been pointed out, for contradictory systems of order to exist at the same time. In that case each is "valid" precisely to the extent that there is a probability that action will in fact be oriented to it."

Max Weber, Basic Sociological Terms, pg.32