When Confucius asked someone to convey his regards to a friend in another state, he would bow twice respectfully before sending the messenger off. When Ji Kangzi sent him medicine, Confucius bowed and accepted it, but said, “I do not yet understand its nature; I dare not taste it.”
The Master said, “You, shall I teach you what knowledge is? When you know a thing, to recognize that you know it, and when you do not know a thing, to recognize that you do not know it. That is knowledge.”