In his view, there were three different types of knowledge during the Renaissance, classical and modern. During the Renaissance, the relationship between words and things was based on the principle of "imitation". In the classical era initiated by the Enlightenment, this relationship was based on the principle of "similarities and differences" and became the basis of grammar, natural history and economic analysis. After the world enters the modern era, people "return to language", and under the influence of the cognitive model of modern humanities, they find that language is a "rude existence". Therefore, in contemporary times, the authenticity of language reflecting the world and existence is increasingly questioned and criticized. Foucault believes that the transformation from the classical discourse and the representation system of things to the modern way has brought about the division of the knowledge system. The knowledge system originally integrated in the name of "science" has been divided into two independent systems, namely, humanities and natural sciences. Finally, Foucault believes that with the development of knowledge system, human knowledge system will still be divided and new knowledge system will appear.