在《道德经》的主页里，老子曰:
In "Tao De Jing" (The Way), Laozi began with these words:

道可道 The Tao that can be spoken of
非常道 is not the enduring and unchanging Tao.
名可名 The name that can be named
非常名 is not the enduring and unchanging name.

如此说法有点自相矛盾。 难怪白居易因此写了一篇《读老子》:
To say so is an oxymoron. It's thus not surprising that in response, Bai Juyi wrote "Reading Laozi":

言者不知知者默 Those who speak do not know, those who know are silent,
此语吾闻于老子 I heard this saying from the old gentleman.
若道老君是知者 If the old gentleman was one who knew the way,
缘何自若五千文 Why did he feel able to write five thousand words?

(Source of poems: Chinese Poems)