He who does not bellow the truth when he knows the truth makes himself the accomplice of liars and forgers.

Péguy’s aphorism frames silence in the face of known falsehood as a form of moral complicity. “Bellow” (rather than merely “say”) stresses that truth-telling may require public, forceful witness, not private assent. The line implies an ethics of responsibility: knowing the truth creates an obligation to speak, because lies and “forgeries” thrive on the passivity of bystanders as much as on the activity of deceivers. In that sense, the quote is less about abstract truth than about civic courage—how communities are corrupted when those who could correct error choose comfort, prudence, or fear instead.