The Han Dynasty doctor Chang Chung-ching in the book Ch'ien Ch'in Yao Fang offers this general principle for those wishing to study medicine: "If you kill for the sake of life, then you're far removed from the true spirit of life.
漢朝醫師張仲景在《千金要方》書中就針對想要習醫的人，提出「…… 夫殺生求生，去生更遠，…… 市有先死者，則市而用之，不在此例，能不用者，斯為大哲」的原則。