… is from pages 457-458 of F.A. Hayek’s profound and important 1964 article “Kinds of Order in Society” (available without charge on-line here) as it appears in Liberty Fund’s 1981 single-volume collection of New Individualist Review (footnote deleted):
The chief difficulty is that the order of social events can generally not be perceived by our senses but can only be traced by our intellect. It is, as we shall say, an abstract and not a concrete order. It is also a very complex order. And it is an order which, though it is the result of human action, has not been created by men deliberately arranging the elements in a preconceived pattern. These peculiarities of the social order are closely connected…. We shall see that, although there is no absolute necessity that a complex order must always be spontaneous and abstract, the more complex the order is at which we aim, the more we shall have to rely on spontaneous forces to bring it about, and the more our power of control will be confined in consequence to the abstract features and not extend to the concrete manifestations of that order.