Jia Yi was a native of Luoyang during the Western Han Dynasty, earning a reputation as a child prodigy; by the time he was eighteen, his essays had already made him famous far and wide.
Emperor Wen of Han heard that Jia Yi was exceptionally talented, so he sent for him to come to the capital and serve as an imperial scholar. At that time, Jia Yi was only twenty years old.
Once, Jia Yi submitted a memorial to Emperor Wen of Han, explaining the principles of governing the state:
"During the Qin Dynasty, the eunuch Zhao Gao taught Qin Shi Huang's second son, Hu Hai, only how to execute prisoners, so what Hu Hai learned was either beheading offenders or exterminating entire clans."
"After Qin Shi Huang died, Hu Hai became emperor. On the very second day of his reign, he began killing people. When someone offered him loyal advice, he deemed it slander; when someone presented strategies for governing the country and pacifying the people, he considered it heresy. He killed people as easily as cutting grass.
"Then, was Hu Hai born so cruel? No. This was entirely the result of unreasonable instruction from his teachers. As the saying goes: 'If you don't know an official, just look at the results of his work, and you will understand!'"
“As the saying goes, 'The overturned cart ahead serves as a warning for the cart behind; seeing the cart ahead fall, the cart behind should take it as a caution!'” “The fall of the Qin Dynasty, like an overturned cart ahead, should serve as our warning for the cart behind!”
Emperor Wen of Han found Jia Yi's memorial so compelling that he promoted him to Grand Master. When the emperor later sought to elevate Jia Yi further, he faced opposition from Zhou Bo, the Marquis of Jiang, and others. Consequently, the emperor appointed Jia Yi as Grand Tutor to the Prince of Changsha, and later transferred him to serve the Prince of Liang. Jia Yi, perpetually frustrated by his unfulfilled ambitions, died at the young age of thirty-two.
Later, the idiom "Lesson from the Overturned Cart" came to mean that previous failures can serve as a warning for the future.
Source: *Book of Han*, "Biography of Jia Yi"
Meaning of the Idiom: Later, the Chinese idiom "前车之鉴" came to describe previous failures can serve as a warning for the future.