… is from page 125 of the original 1960 Harvard University Press edition of Frank Knight’s collection of lectures, delivered in 1958 at the University of Virginia, titled Intelligence and Democratic Action:
Human society is basically a phenomenon of more or less stable beliefs and patterns of conduct. The principle of [classical] liberalism is that these are not fixed once and for all – historically through prescription by some supernatural (or charismatic) authority – but are always subject to question, discussion, and alteration by agreement. Free society thus stands for progress, and also allows for and approves of much variety in both belief and conduct.