… is from page 253 of F.A. Hayek’s March 23rd, 1966, lecture delivered to the British Academy and titled “Dr Bernard Mandeville,” as this lecture is reprinted in Hayek’s 1978 collection, New Studies in Philosophy, Politics, Economics and the History of Ideas:
His [Mandeville’s] main contention became simply that in the complex order of society the results of men’s actions were very different from what they had intended, and that the individuals, in pursuing their own ends, whether selfish or altruistic, produced useful results for others which they did not anticipate or perhaps even know; and, finally, that the whole order of society, and even all that we call culture, was the result of individual strivings which had no such end in view, but which were channeled to serve such ends by institutions, practices, and rules which also had never been deliberately invented but had grown up by the survival of what proved successful.