The Doctrine of the Mean teaches: "The gentleman governs people by treating them as they are, and stops when they reform. Loyalty and reciprocity are not far from the Way. What you would not want imposed on yourself, do not impose on others."
The phrase "以其人之道还治其人之身" (treat them as they treat you) became the Chinese idiom for poetic justice — responding to someone using their own methods. It is not revenge; it is a mirror.
故君子以人治人，改而止。忠恕违道不远，施诸己而不愿，亦勿施于人。
故君子以人治人，改而止。忠恕违道不远，施诸己而不愿，亦勿施于人。
Reflection & Analysis · 寓意解读
Core Wisdom
The mirror does not judge — it simply reflects. If you do not like what you see, change your face, not the mirror.
This teaching is often confused with revenge, but it is actually about empathy through experience. The person who lies and is then lied to understands, for the first time, what lying feels like. The person who bullies and is then bullied learns what bullying costs.
The Doctrine of the Mean's version is gentler: "stop when they reform." The mirror is not permanent — it is a teaching tool. Once the lesson is learned, the mirror can be put away.