The liar's punishment is not in the least that he is not believed, but that he cannot believe anyone else.

The aphorism frames lying as a self-inflicted moral and psychological injury rather than merely a social offense. Shaw suggests that the deepest consequence of habitual deception is not external—loss of reputation or credibility—but internal: the liar’s own capacity for trust erodes. Having learned to manipulate truth, the liar projects the same motives onto others, reading sincerity as strategy and testimony as performance. The result is a lonely, defensive worldview in which relationships cannot be secure because belief itself has been poisoned. The line also implies a broader ethical claim: truthfulness sustains the social fabric by making mutual confidence possible; to lie is to sabotage the very conditions that allow one to live among others without constant suspicion.