知人知面不知心 [ㄓ ㄖㄣˊ ㄓ ㄇㄧㄢˋ ㄅㄨˋ ㄓ ㄒㄧㄣ; zhi1 ren2 zhi1 mian4 bu4 zhi1 xin1] one may know a person for a long time without understanding his true nature ◄ ►