lài yǔ Xīshī, dào tōng wéi yī 厉与西施，道通为一
A Scabby Person and the Beautiful Lady Xishi Are the Same in the Eyes of Dao.
This is a famous statement made by Zhuangzi on how beauty is relative. Originally it meant there was no difference between a beauty and an ugly person, because they both came from and reflected Dao. The character 厉 (lai) meant 癞 (lai, covered in scabs) in ancient Chinese. Whether a person is beautiful or ugly is but a subjective perspective in the mind of the beholder. Besides, beauty can turn into ugliness, and vice versa. Zhuangzi, from the perspective of the origin of all things, stressed that beauty and ugliness are both in accord with Dao and are inherently the same. This idea has encouraged later literary critics to look at all things, including literary works, from the perspective that opposite things complement each other.
In the light of Dao, a small blade of grass or a tall pillar, someone as ugly as a favus patient or someone as beautiful as Lady Xishi, as well as crafty and strange things, are all the same. (Zhuangzi)
Dao manifests in an array of objective things, but its genuine spirit lies within them. (Sikong Tu: Twenty-Four Styles of Poetry)