Conscience is the inner voice that warns us somebody may be looking.

Mencken’s quip treats “conscience” less as an innate moral compass than as a social reflex: the feeling of guilt or restraint arises because we fear exposure, judgment, or punishment. The joke hinges on reducing lofty ethical language to a practical concern—being caught—thereby satirizing moral self-congratulation and conventional piety. Read this way, the line suggests that much of what passes for virtue is compliance shaped by surveillance (real or imagined) and reputation management. It also implies a skeptical view of moral education: people may behave “well” not from principled conviction but from anxiety about consequences and public scrutiny.