In John Flanagan’s Ranger’s Apprentice series, book 2, the Burning Bridge, he quoted an old Celtic saying through Halt, the Ranger’s mouth: “One man may be deceit. Two can be conspiracy. Three is the number I trust.” I don’t know if this has been made up by john or come out of REAL Celtic saying, but obviously the wisdom of human beings are similiar, no matter how far they are separated, Ancient China in far east and Old Celtic in far west.
The king of Wei’s minister, Pang Cong, and the crown prince (the heir apparent to the king of Wei) were to become hostages at Handan.
Before leaving, he asked the king of Wei, “Now if one person said that there was a tiger in the market, would your majesty believe it?”
The king said, “No.”
Then, Pang Cong said, “If two people said that there was a tiger in the market, would your majesty believe it?”
The king responded, “I would be suspicious about it.”
Finally, Pang Cong asked, “If three people said that there was a tiger in the market, would your majesty believe it?”
The king replied, “I would believe it.”
Pang Cong said, “Whereas it is clear that there is no tiger in the market, yet three people saying so produces the tiger. Now then, Handan is further away from Daliang (the capital of the state of Wei) than the market, and the number of people that will slander me will be more than three. I hope that your majesty is able to see that!”
The king said, “I already know that without you having to tell me.”
Thus, he bid the king farewell, but the slander had already started.
Later on, the crown prince was released, but Pang Cong was not granted an audience with the king of Wei.
(Source: Wiktionary translation)