From F. A. Hayek’s “Principles or Expediency?”:
What helpful insight science can provide for the guidance of policy consists in an understanding of the general nature of the spontaneous order, and not in any knowledge of the particulars of a concrete situation, which it does not and cannot possess. The true appreciation of what science can contribute to the solution of our political tasks, which in the nineteenth century was fairly general, has been obscured by the new tendency derived from the now fashionable misconception of scientific method: the belief that science consists of a collection of particular observed facts, which is erroneous so far as science in general is concerned, but doubly misleading where we have to deal with the parts of a complex spontaneous order. Since all the events in any part of such an order are interdependent, and an abstract order of this sort has not necessarily any recurrent concrete parts which can be identified by individual attributes, it is necessarily vain to try to discover by observation regularities in its parts. The only theory which in this field can claim scientific status is the theory of the order as a whole; and such a theory (though it has of course to be tested on the facts) can never be achieved inductively by observation but only through constructing mental models made up from the observable elements.
F. A. Hayek, “Principles or Expediency?”, Toward Liberty: Essays in Honor of Ludwig von Mises on the Occasion of his 90th Birthday, vol. 1, ed. F.A. Hayek, Henry Hazlitt, Leonrad R. Read, Gustavo Velasco, and F.A. Harper (Menlo Park: Institute for Humane Studies, 1971).