Zai Yu (522-458 BCE), with the surname Zai, given name Yu, and courtesy name Ziwo, also known as Zai Wo, was twenty-nine years younger than Confucius and a native of the State of Lu. He is mentioned five times in The Analects. Gifted with intelligence, resourcefulness, eloquence, and persuasive skills, Zai Yu was listed among the "Four Disciplines and Ten Philosophers" (in the category of Speech) of Confucius's school. He once accompanied Confucius on his travels through various states; during these journeys, Confucius often sent him on diplomatic missions, such as "to Qi" and "to Chu," showing great trust in his abilities. In the sixth year of Duke Ai of Lu (489 BCE), after escaping the predicament in Chen and Cai, Confucius and his disciples arrived in Chu. King Zhao of Chu intended to employ Confucius and grant him a fief of seven hundred li of land from the Book Society. However, Prime Minister Zixi of Chu objected, asking the king, "Is there any official in your court as capable as Zai Yu?" The king replied no. Zixi said, "If Confucius gains territory, with his disciples as aides, it would not be Chu's fortune." King Zhao then abandoned his plan. Chu was a large state with many talents, yet King Zhao admitted none of his ministers matched Zai Yu's abilities, highlighting his extraordinary talent and renown among the feudal states.
Zai Yu had his own opinions on matters and often discussed questions with Confucius, demonstrating considerable independent thinking and unique insights. Mencius praised him, saying, "His wisdom is sufficient to recognize a sage." He proposed changing the "three-year mourning period" to a "one-year mourning period," shortening the mourning duration, which drew Confucius's criticism that he was "not Ren (Benevolent)." Zai Yu was intellectually active, fond of learning and deep thinking, and once posed a dilemma to Confucius: if a Ren (benevolent) person fell into a well, and another Ren person was told, what should the latter do? Jumping in would lead to death, but not jumping in would mean failing to save someone in need. Confucius thought Zai Yu's question was problematic and said, "Why must it be so? A Junzi (Exemplary Person) can be made to go to a place but cannot be trapped; can be deceived but cannot be fooled." He believed Zai Yu was trying to trick him. Confucius felt Zai Yu's words and actions were inconsistent, saying, "Judging people by their words, I made a mistake with Zai Yu," and from Zai Yu, he changed his previous shortcomings, now observing people's actions when listening to their words.
Once, Zai Yu (a disciple of Confucius) was caught sleeping during the day and was harshly scolded by Confucius as "rotten wood" and "a wall of dung and dirt." Although Confucius criticized him more than any other disciple, Zai Yu still held boundless admiration for his teacher, saying, "In my view of the Master, he is far more worthy than Yao and Shun (legendary sage kings)." (Mencius, Gongsun Chou, Part 2) Later, he served as the Grand Steward of Linzi in the State of Qi and was killed for his involvement in the assassination of the ruler by Chen Heng (also known as Tian Chang).