A belief is not true because it is useful.

Amiel draws a sharp line between the practical benefits of an idea and its correspondence to reality. A belief may steady the nerves, unify a community, or motivate virtuous action, yet still be false; usefulness is not a proof. The remark is a warning against self-deception and against treating “what works for me” as equivalent to “what is true.” It also anticipates later philosophical disputes about pragmatism: even if some beliefs have instrumental value, truth requires independent justification—evidence, coherence, or other epistemic warrants—rather than mere utility. The quote champions intellectual integrity over comfort.