… is from page 172 of F.A. Hayek’s 1950 essay “Economics,” written for Chambers’s Encyclopaedia, as this essay is reprinted as chapter 11 in Essays on Liberalism and the Economy (2022), which is volume 18 (expertly edited by the late Paul Lewis), of The Collected Works of F.A. Hayek (footnote deleted):
There is ground for doubt whether we shall ever be able fully to explain why individuals act as they do; and in so far as we can arrive at valid generalisations about the causes of human action, this is a task for psychology and not for economics. The specific problem of economics and of all social theory is not why people act as they do, but what are the unintended consequences of their actions when they live in societies in which the individuals and groups act according to their own individual decisions and plans.
Hayek died on this date, March 23rd, in 1992, about six weeks shy of his 93rd birthday.