If you think anyone is sane you just don't know enough about them.

The line plays on the gap between public persona and private reality: the more intimately you know someone, the more you encounter contradictions, irrationalities, and coping mechanisms that don’t fit tidy notions of “normal.” It satirizes the cultural impulse to sort people into sane/insane categories, suggesting that “sanity” is often just ignorance of another person’s interior life. In Moore’s comic mode, the remark also functions as a leveling joke—everyone is odd up close—inviting tolerance and humility in judgment. The humor depends on exaggeration, but the underlying point is serious: human behavior is messy, and certainty about others is usually overconfidence.