Doubt Is Not A Pleasant Condition

This remark appears in a letter dated November 28, 1770, to Frederick William, Prince of Prussia — the future Frederick William II — not to Frederick the Great himself, despite the common attribution. Voltaire wrote it while criticizing Baron d'Holbach's atheist work Système de la Nature (1770), which he found as dogmatically certain in its denial of God as the theologians were in affirming one. Voltaire was a lifelong deist, not an atheist, and the line captures his core epistemological position: intellectual humility is a virtue; confident claims to have resolved ultimate questions are not.