… is from page 60 of F.A. Hayek’s July 1946 speech at Stanford University titled “The Prospects of Freedom,” as this speech appears – for the first time in print – as chapter 3 of Essays on Liberalism and the Economy, which is volume 18 of The Collected Works of F.A. Hayek (Paul Lewis, ed., 2022) (emphasis added):
[W]e shall not prevent the gradual advance of totalitarian control if we do not succeed in defeating the philosophy which produces it.