His emphasis on prediction of the principle or pattern leaves out a great deal. It is not merely that only general predictions can be made—it is that predictions often can be made only of best-guess probabilities, not even of patterns or principles. As Hayek mentioned, patterns can sometimes be expressed numerically as ranges.

Hayek's Journey: The Mind of Friedrich Hayek (2003) - Ch. 10 : Epistemology, Psychology, and Methodology