Gǔjí zhōng rú shì shuō, hòurén jiē fèng wéi jīngdiǎn.
The ancient texts said as much, and later generations treated it as canon.
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如是说 is best known as part of 查拉图斯特拉如是说, the Chinese title for Nietzsche's 「Also sprach Zarathustra」 (Thus Spoke Zarathustra). The phrase echoes classical Chinese Buddhist and Confucian text idioms meaning 「it is as follows.」