… is from page 192 of Karl Popper’s 1969 paper “A Pluralist Approach to the Philosophy of History,” which is a chapter in the 1969 collection Roads to Freedom: Essays in Honour of Friedrich A. von Hayek (Erich Streissler, Gottfried Haberler, Friedrich A. Lutz, and Fritz Machlup, eds.):
[G]etting educated is getting an inkling of the immensity of our ignorance.
