… is from page 263 of F.A Hayek’s 1958 profound paper “The Creative Powers of a Free Civilization,” which is Chapter 9 in Essays on Individuality, Felix Morley, ed. (Indianapolis: Liberty Press, 1977 ):
The whole conception of man, already endowed with a mind capable of conceiving civilization, set out to create that civilization as it was already preformed in his mind, is fundamentally false. Man does not simply impose upon nature a preformed mental pattern. His mind is itself a pattern constantly changing as a result of his endeavor to adapt himself to his surroundings. It is equally misleading to think that to achieve a higher civilization we have merely to put into effect the ideas now guiding us. If we are to advance there must be room for a continuous revision of our present conceptions and ideals as a result of further experience. We are as little able to conceive what civilization will be, or can be, five hundred or even fifty years hence as medieval man, or even our grandparents, were able to foresee our own manner of life.