三寸之舌 A Three-Cùn Tongue
有蓍作筮？憑書句斷人禍福？」行者道：「我一毫不用，只是全憑三寸舌，萬事盡皆知。」太子道：「這廝又是胡說。自古以來，《周易》之書，極其玄妙，斷盡天下吉凶，使人知所趨避，故龜所以卜，蓍所以筮。聽汝之言，憑據何理？妄言禍福，扇惑人心。」有蓍作筮？凭书句断人祸福？」行者道：「我一毫不用，只是全凭三寸舌，万事尽皆知。」太子道：「这厮又是胡说。自古以来，《周易》之书，极其玄妙，断尽天下吉凶，使人知所趋避，故龟所以卜，蓍所以筮。听汝之言，凭据何理？妄言祸福，扇惑人心。」
逐句解 Line by line
Have you milfoil for your yarrow-casting?
The second orthodox instrument. 蓍 shī is milfoil or yarrow, whose dried stalks are counted out to build a hexagram; 筮 shì is that method of divining, as against 卜 bǔ with the shell. The prince is running through the canonical list.
Do you rely on the words of a book to judge men’s weal and woe?”
Third possibility, and the most modern: are you working from a manual? 斷人禍福 is to judge a person's fortune and misfortune.
Pilgrim said, “I use not a hair of them; I rely wholly on my three-cùn tongue, and all ten thousand matters are entirely known to me.”
The answer refuses all three. 三寸舌 — a tongue three 寸 long, each cùn a tenth of a chǐ — is the standing idiom for eloquence, and specifically for talking one's way into or out of anything; it belongs to persuaders and envoys, not diviners. Wukong is answering a question about method with a boast about rhetoric. 一毫不用 is "not a hair of it"; 盡皆知 has 盡 as jìn, wholly.
The prince said, “This fellow talks nonsense again.
這廝 — "this fellow" — is contemptuous, the word for someone beneath discussion. 胡說 is talking rubbish.
From of old, the Book of Changes has been most subtle and profound, judging to the full the fortunes of all under heaven, and letting men know what to seek and what to shun; thus the tortoise-shell is the means of divining, and the milfoil the means of yarrow-casting.
And now the prince makes his case properly, and it is a serious one. The 周易, the Book of Changes, is the oldest of the classics and the foundation of legitimate prognostication; shell and stalk are its authorised instruments. 趨避 is what to seek and what to shun — divination as practical guidance, not fortune-telling. 斷盡 has 盡 as jìn; 龜所以卜 keeps 卜 as bǔ.
To hear your words — on what principle do they rest?
The demand underneath the whole speech: on what authority? 憑據何理 — resting on what principle.
You speak recklessly of weal and woe, inciting and deluding men’s hearts.”
And the charge, which is a legal one in the making. 妄言禍福 is reckless talk about fortune and disaster; 扇惑人心 is to fan up and delude the popular mind — the standard formula for prosecuting an unlicensed prophet, and exactly what a court would put in the indictment. The sealed note reads 扇 here as shān, to fan up (the sense usually written 煽), against the ruby's shàn.
The prince meets the oracle the way a Confucian-trained student would: he names the Book of Changes, lists its authorised instruments — tortoise-shell for one method, milfoil stalks for the other — and asks by what method this manikin claims to know anything. It is not snobbery. Divination was a serious discipline with a canonical text behind it, and he is asking for credentials.
Wukong's answer sets his own kind of knowing against the entire apparatus: not a hair of shell or stalk, only a three-cùn tongue, and everything known. It is worth noticing that this is an eloquence idiom, not a divination one — he is claiming to be a talker, not a seer. The prince, unmoved, charges him with reckless prophecy that inflames the popular mind, which is the language of a criminal charge. Only one thing will break this deadlock, and it is not argument: it is the boy's own history.