Quotations about:
    ruse

My dear brothers, when you hear the progress of enlightenment extolled, never forget that the devil’s cleverest trick is to persuade you that he does not exist!

[Mes chers frères, n’oubliez jamais, quand vous entendrez vanter le progrès des lumières, que la plus belle des ruses du diable est de vous persuader qu’il n’existe pas!]

Charles Baudelaire (1821-1867) French poet, essayist, art critic

Le Spleen de Paris (Petits Poèmes en Prose), No. 29 “The Generous Gambler [Le Joueur généreux]” (1869) [tr. Kaplan (1989)]
    (Source)

A warning by a Parisian preacher, as reported by the Devil himself. Used in movie The Usual Suspects (1995) as "The greatest trick the Devil ever pulled was convincing the world he didn't exist."

(Source (French)). Alternate translations:

My dear brethren, never forget, when you hear the progress of wisdom vaunted, that the cleverest ruse of the Devil is to persuade you he does not exist!
[tr. Shipley (<1919) "The Generous Player"]

My dear brethren, never forget, when you hear boasts about the progress of enlightenment, that the finest ruse of the devil is to persuade you that he does not exist!
[tr. Hamburger (1946) "The Generous Gamester"]

My dear brothers, never forget when you hear people boast of our progress in enlightenment, that one of the devil's best ruses is to persuade you that he does not exist!
[tr. Varèse (1970)]

The Devil's subtlest ruse is to convince us that he doesn't exist.
[tr. McGowan (1993)]

Dear brethren, never forget that the finest of all the devil's tricks is to persuade you that he doesn't exist.
[tr. Lerner (2003)]

My dear brethren, do not ever forget, when you hear the progress of lights praised, that the loveliest trick of the Devil is to persuade you that he does not exist!
[Source]