How easy it would have been flatly to have told the boy that his pilgrim was only an old tramp of some kind, and then to have commanded him not to think otherwise. But by allowing the boy to see that a question was possible, he had rendered such a command ineffective before he uttered it. Insofar as thought could be governed at all, it could only be commanded to follow what reason affirmed anyhow; command it otherwise, and it would not obey.

Ch 4 - A Canticle for Leibowitz (1959) - Fiat Homo