… is from Bertrand de Jouvenel’s 1960 Earl Grey Memorial Lecture, “Efficiency and Amenity”; specifically, it’s from page 103 of the 1969 reprint of this lecture in A.E.A. Readings in Welfare Economics (Kenneth J. Arrow and Tibor Scitovsky, eds.):
A lot of things can be reckoned out on paper which cannot happen in reality.
