The most important theoretician of the Legalist school of thought, also known as the School of Law, is Han Feizi. He was born as a prince in the ruling family of the state of Han. Han Feizi drew up plans for Han to increase its power, but the Han ministers did not utilize them, so he concentrated on writing essays on his philosophy of government. In 233 B.C. the state of Han sent him on a mission to the neighboring state of Qin, whose power threatened Han, and the Qin king apparently decided to give Han Feizi a position in his own government. One of the Qin king's ministers, Li Si, removed his rival by imprisoning Han Feizi and forcing him to commit suicide with poison.

Han Feizi and Li Si had both been fellow students of Xunzi, then the leading philosopher in the Confucian school of thought. Li Si later became the first prime minister of the Qin dynasty (221-206 BC) under Emperor Qin Shi Huang, who brutally employed Legalist principles to create a centralized Chinese state. Confucian scholars attributed the rapid collapse of the Qin to the principles of Legalism, which they despised, although they appreciated the practical recommendations for government put forth in Legalist manuals.