There is no witness so dreadful, no accuser so terrible as the conscience that dwells in the heart of every man.

Attributed to the Greek historian Polybius, this maxim frames conscience as an internal tribunal more fearsome than any external court. The “witness” and “accuser” imagery suggests that wrongdoing carries its own inescapable evidence: the mind’s awareness of guilt. In this view, moral accountability is not primarily enforced by laws or public opinion but by an inner faculty that continually judges one’s actions. The line also implies universality (“every man”), presenting conscience as a shared human endowment and a stabilizing force in ethical life—capable of restraining misconduct even when no one else is watching.