The great Kwan-tsz insisted on his prince carrying out a treaty which had been extorted in times of stress; but, as a rule, the most opportunistic principles were laid down, even by Confucius himself when he was placed under personal stress: "Treaties obtained by force are of no value, as the spirits could not then have really been present." In 589 Ts'u invaded the state of Wei, just mentioned, and menaced the adjoining state of Lu, compelling the execution of a treaty. Confucius, who once broke a treaty himself, naturally retrospectively considered this ducal treaty of no effect, and he even goes so far as to avoid mentioning in his annals some of the important persons who were present; he especially "burkes" two Chinese ruling princes, who were shameless enough to ride in the same chariot with the King of Ts'u, under whose predominancy they were, and who were therefore themselves under a kind of stress. In 482 one of Confucius' pupils made the following casuistical reply to the government of Wu on their application for renewal of a treaty with her: "It is only fidelity that gives solidity to treaties; they are determined by mutual consent, and it is with sacrifices that they are laid before our ancestors; the written words give expression to them, and the spirits guarantee them. A treaty once concluded cannot be changed: otherwise it were vain to make a new one. Remember the proverb: "What needs warming up more may just as well be eaten cold." The ordinary rough-and-ready form of oath or vow between individuals was: "If I break this, may I be as this river"; or, "may the river god be witness." There were many other similar forms, and it was often customary to throw something valuable into the river as a symbol. CHAPTER XIX CONFUCIUS AND LITERATURE