《淮南子·人间训》
变化外形是为了适应世俗，内心不变是为了保全自身。所以一个人如果内心有固定操守，外表又能屈能伸、能盈能缩、能卷能舒，与物推移周旋，那么干什么都不会陷入困境。
得道之士，外化而内不化，外化，所以入人也，内不化，所以全其身也。故内有一定之操，而外能诎伸、赢缩、卷舒，与物推移，故万举而不陷。
Changing the external form is for the purpose of adapting to the world. Keeping the heart and mind unchanged is for the purpose of preserving oneself. Therefore, if a person’s heart and mind have a firm course of action but their external appearance is flexible, can become full or empty, can roll up or unfurl, and can get along with changes in things, then they will not fall into a difficult situation no matter what they do.