《淮南子·说山训》
人看到中间掏空的木头能浮在水面而明白了造船的原理，人看到了飞蓬随风转动而知道了造车的原理，人看到鸟的足迹而知道创造文字以著书，这些创造发明都是用类推的大法而取得的。
见窾木浮而知为舟，见飞蓬转而知为车，见鸟迹而知著书。以类取之。
People saw that a hollowed-out log could float on water and so understood the principle of building boats; people saw dandelions spinning in the wind and so learned the principle of building carriages; people saw the footprints of birds and so learned to create characters to write books; these creations and inventions were all achieved by using the great method of analogy.