In Ludwig Feuerbach and the End of German Classical Philosophy, Engels pointed out that "The major fundamental problem of all philosophy, especially modern philosophy, is the relationship between thinking and being." As a fundamental question of philosophy, from an epistemological point of view, different answers to whether thinking and being are identical can be divided into cognosciblism and agnosticism. In Hegel's philosophy, based on the ego movement of absolute spirit, he adheres to the view of cognosciblism, and regards thought as the subject of active development, in the process of development, thought externalizes itself into existence and opposes it, and then sublates this opposition back to itself, that is, because of its initiative and creativity, thought creates existence, and existence is the externalization of thought. The process by which the mind transcends itself and diverges, and finally returns to itself, is the process by which thought and being are one. At the same time, Hegel's epistemology does not absolutely oppose the materialist epistemology, but regards it as a link of its own epistemology. It can be seen that Hegel not only expounds the identity of thought and existence on the basis of idealism, but also the development process of concept revealed in his whole logic system is exactly such a process of the same thought and existence, and in the process of analyzing his cognosciblism, it reflects the dialectical unity of logic, epistemology, ontology and dialectics in Hegel's philosophy.