《庄子·杂篇·庚桑楚》
婴儿整天啼哭咽喉却不会嘶哑，这是因为声音谐和自然达到了顶点；婴儿整天握着小手而不松开，这是因为听任小手自然地握着乃是婴儿的天性与常态；婴儿整天瞪着小眼睛一点也不眨眼，这是因为内心世界不会滞留于外界事物。
儿子终日嗥而嗌不嗄，和之至也；终日握而手不掜，共其德也；终日视而目不瞬，偏不在外也。
A baby cries all day long but its throat does not become hoarse, because its voice is in harmony with nature and has reached its peak; a baby holds its little hands together all day long and does not let go, because it is letting its little hands grasp naturally, which is the nature and normality of a baby; a baby stares wide-eyed all day long and does not blink, because its inner world does not linger on external things.