… is from page 376 of the 2014 collection, The Market and Other Orders (Bruce Caldwell, ed.), of some of F.A. Hayek’s essays on spontaneous-ordering forces; specifically, this quotation is from Hayek’s previously unpublished 1961 lecture at the University of Virginia “The Object of Economic Theory” (which is the first of four lectures that Hayek delivered in UVA’s Newcomb Hall during the Spring 1961 semester; the title of this lecture series by Hayek is “A New Look at Economic Theory”):
There seems to me to be still much truth in the view that as we move from the comparatively simple phenomena of inanimate nature to the increasingly complex ones of life and society, we may have to become more modest in our aims and be content with results which are more limited in their predictive content than is the case in the physical sciences.