To be enlightened: a big phrase! Certain men think themselves enlightened because they are decided: thus taking conviction for truth, and strong conception for intelligence. There are others who, because they know all the words, think they know all the truths.
 
[Être éclairé, c’est un grand mot! Il y a certains hommes qui se croient éclairés, parce qu’ils sont décidés, prenant ainsi la conviction pour la vérité, et la forte conception pour l’intelligence. Il en est d’autres qui, parce qu’ils savent tous les mots, croient savoir toutes les vérités.]

Joseph Joubert (1754-1824) French moralist, philosopher, essayist, poet

Pensées [Thoughts], ch. 4 “De la Nature des Esprits [On the Nature of Minds],” ¶ 36 (1850 ed.) [tr. Calvert (1866), ch. 5]
    (Source)

(Source (French)). Alternate translations:

Enlightenment -- a great word! Some men think themselves enlightened, because they are decided, taking conviction for truth, and strong conception for intelligence. Others, because they know all that can be said think that they know all truth.
[tr. Lyttelton (1899), ch. 3, ¶ 15]

Enlightenment is a fine word! Some men fancy themselves enlightened because they are decisive, thus taking conviction for truth, and force of conception for intelligence. Others think that because they have every word at their command, they have every truth also.
[tr. Collins (1928), ch. 4]

Because they know all the words, they think they know all the truths.
[tr. Auster (1983)], 1819 entry]