“Beware of the man who works hard to learn something, learns it, and finds himself no wiser than before.”

Source: The Urth of the New Sun

Source: Irrational Man: A Study in Existential Philosophy (1958), Chapter Six, The Flight From Laputa, p. 128

Attributed in You Vs. You: Sport Psychology Got Life (2005) by Wayne Mazzoni, p. 90
2000s

Book V, fable 9, line 4.
Fables

Source: The Purpose Driven Life: What on Earth Am I Here for?

Reason: A Poem, 1700.

Account of his famous dream of the benzene structure, as quoted in A Life of Magic Chemistry : Autobiographical Reflections of a Nobel Prize Winner (2001) by George A. Olah, p. 54<!-- also partially quoted in Serendipity, Accidental Discoveries in Science (1989) by Royston M. Roberts , pp. 75-81 -->
Context: I was sitting writing on my textbook, but the work did not progress; my thoughts were elsewhere. I turned my chair to the fire and dozed. Again the atoms were gamboling before my eyes. This time the smaller groups kept modestly in the background. My mental eye, rendered more acute by the repeated visions of the kind, could now distinguish larger structures of manifold conformation; long rows sometimes more closely fitted together all twining and twisting in snake-like motion. But look! What was that? One of the snakes had seized hold of its own tail, and the form whirled mockingly before my eyes. As if by a flash of lightning I awoke; and this time also I spent the rest of the night in working out the consequences of the hypothesis. Let us learn to dream, gentlemen, and then perhaps we shall learn the truth... but let us beware of publishing our dreams before they have been put to the proof by the waking understanding.

Source: Works and Days and Theogony