“It is unsafe to take your reader for more of a fool than he is.”

... un auteur ne nuit jamais tant à ses lecteurs que quand il dissimule une difficulté.
in the preface of Deux mémoires d'Analyse pure, October 8, 1831, edited by [Jules Tannery, Manuscrits de Évariste Galois, Gauthier-Villars, 1908, 27]

Source: King Lear

A Narrative of Some of the Lord's Dealings with George Müller Written by Himself, Third Part.
Third Part of Narrative

Source: Don Quixote de la Mancha (1605–1615), Part I, Book IV, Ch. 4.

Plutarch's Life of Cato
Variant: Wise men profit more from fools than fools from wise men; for the wise men shun the mistakes of fools, but fools do not imitate the successes of the wise.

As quoted in One Big Fib : The Incredible Story of the Fraudulent First International Bank of Grenada (2003) by Owen Platt, p. 37

Song Alfie