Li was a scientist of political intrigue. He wrote: "When you conceal your will from others, that is Thick. When you impose your will on others, that is Black." Thick Black Theory describes the ruthless, hypocritical means men use to obtain and hold power: "thick faces" , "black heart" . It went through several printings before being banned in China as subversive.
Li argued that "A great hero is no more than a person who is impudent and wicked." According to Li, the wickedest of all was Cao Cao. "I would rather betray someone than be betrayed." It shows how black Cao Cao' s heart was inside. Li picked Liu Bei as the highly-skilled person with a "thick face". He never thought it shameful to live inside another's fence. He was also a frequent crier, appealing to others' sympathy. There is even a saying, "Liu Bei's JiangShan was obtained through his crying."
Before the Cultural Revolution, Mao Zedong studied "Houheixue" which is the "Thick Black Theory". Hou means "thick face" in Chinese; it means having a thick hide. Hei means black in Chinese; it means having a black heart. During the 1980s, news spread that Mao had studied the Thick Black Theory and Li Zhongwu was in the spotlight again. In Beijing during the 1990s, many books related to the Thick Black Theory, "thick-black-ology",, were published.