Franklin personifies vice as something aware of its own ugliness and therefore anxious to conceal it. The “mask” represents the excuses, respectable appearances or misleading explanations that can make wrongful conduct seem more acceptable than it really is. The saying suggests that wrongdoing is often presented under a more favourable description rather than defended openly as wrongdoing.

The maxim is therefore concerned with moral judgement as well as deception. People may describe selfishness as prudence, cruelty as firmness or dishonesty as necessity in order to make questionable behaviour easier to defend. Franklin’s broader point is that appearances and stated motives should not be accepted uncritically. Ethical judgement requires attention to the substance and consequences of an action, not merely to the attractive language used to justify it.