Every man is best known to himself.

A person has the closest knowledge of their own thoughts, motives, feelings, and private conduct. Others may observe actions, but cannot fully see the reasons and experiences behind them.

The saying can stress self-awareness and responsibility for self-judgment, while cautioning against conclusions based only on appearances or reputation. It does not necessarily claim that people assess themselves accurately or without bias.

Use it when contrasting someone’s inner knowledge with the limited view available to others, especially when discussing motives, character, or private experience. Its traditional generic use of “man” may sound dated in contemporary inclusive prose.