Han Feizi and Li Si studied together under the Confucian philosopher Xunzi, and the two men's later careers make one of the starkest cautionary stories in classical Chinese thought. Both moved toward Legalism rather than the Confucian teaching of their shared master, but where Li Si became a powerful minister at the Qin court, rising to help draft the administrative machinery of the newly unified empire, Han Feizi, a member of the ruling family of the smaller state of Han, wrote as an outside critic and theorist, synthesizing the separate emphases of earlier Legalist thinkers, Shang Yang's codified law, Shen Buhai's administrative technique, and Shen Dao's doctrine of positional power, into a single coherent account of how a state should be governed by ordinary rulers rather than sages. His essays reportedly reached the king of Qin, the future First Emperor, who is said to have declared he would die without regret if he could meet the man who wrote them.
When Han, threatened militarily by Qin, sent Han Feizi on a diplomatic mission around 233 BCE, the king's admiration briefly made him a person of real influence at a rival court, a position ancient accounts describe Li Si undermining through court intrigue against his former classmate, whom he may have seen as a threat to his own standing. Han Feizi was imprisoned and, before the matter could be resolved, forced to drink poison and died in custody.
Qin's eventual unification of China in 221 BCE was administered largely on Legalist principles under Li Si, so the ideas that killed Han Feizi also, through his rival's hand, shaped the first Chinese empire.