《文心雕龙·总术》
如果不能截断弯曲的树根，那就无法考验刀锯是否锋利；同样，如果不能分析深刻的写作道理，也就不能看出作者是否有妙才。
夫不截盘根，无以验利器；不剖文奥，无以辨通才。
If one cannot cut off the curved roots of a tree, then one cannot test the sharpness of a saw; similarly, if one cannot analyze the profound principles of writing, then one cannot see whether an author has a gift.