Once a senior official of the Zheng state, and a contemporary of Confucius, he is regarded as China's earliest recorded lawyer, known for his clever use of words and language in lawsuits.
The Zuo Zhuan and Annals of Lü Buwei critically credit Deng with the authorship of a penal code, the earliest known statute in Chinese criminology entitled the "Bamboo Law".
With arguments pertaining to forms and names, Deng Xi is cited by Liu Xiang for the origin of the principle of xingming, referring to a matching of ministerial words and results.
Depicted as taking both sides of his cases, he is said to have argued for the permissibility of contradictory propositions, likely engaging in hair-splitting debates on the interpretation of laws, legal principles and definitions.
"[8] Deng attracted many clients seeking legal advice, and apparently charging for cases in articles of clothing, he would eventually have enough to count himself rich.
There's certainly nowhere else they can buy the body.”[10][11][12] Despite this portrayal, more modern scholars consider that, having taken the time to write his own penal code, Deng may have been a well-intentioned legal reformer opposing what he saw as the suppression of ideas and opinions.
Xunzi's primary complaint about the two was that they didn't conform to ritual and "righteousness", or the "facts about right and wrong", portraying him as a talented person who, neglecting the way of Confucian morality, wasted his time on pointless intellectual games and sophistry.