If you want to find a philosopher to link German classical philosophy with Marxist philosophy, the most suitable candidate is Hegel. It is not easy for this arrogant and obscure philosopher to have a panoramic understanding of his theory, and even some of Marx's criticisms are based on his misreading. But in the book Philosophy of History (actually a lecture), we have been able to have a relatively simple grasp of its main philosophical system.

In Kant's system, the discussion about the boundary of reason stays in a set of antinomy about God. In this set of antinomy, reason can neither be incompetent nor omnipotent. In Hegel, it was by giving the definition of "reality" that the boundary was found for reason.

In order to explain Hegel's abstract concept clearly, we might as well give an example of a shepherd: when a shepherd counts sheep, he may find that he has lost one. This is because he is riding a sheep. When he comes down from the flock, he can grasp the small-scale whole of the "flock" (naturally biased relative to the larger whole, such as the world). In other words, the shepherd's reason has the potential to complete the behavior of "counting sheep"

But what if we change the scene? If a group of people form a ring and the elements in the set change from sheep to people, then everyone loses the potential to grasp the whole (reason touches the boundary). The reason is realism: in the former example, "man to sheep" will not be bound, but in the latter example, when the situation becomes "man to man", the bondage of realism will be reflected.

At this point, conditional and formal logic philosophy has completely failed in Hegel. When Kant's rationality was discovered at the boundary, Hegel defined the concepts of "world spirit" and "absolute rationality" in his philosophy. As for the individual events in the long history, they have all become the embodiment of the world spirit.

It should be emphasized that the "world spirit" here is different from the hard definitions of "God", "thing itself" and "moral law" in traditional metaphysics (represented by Kant), and traditional metaphysics still stays in conditional formal logic. In Hegel's view, the world spirit is embodied in the form of flow. As for historical events and historical figures, they are the embodiment of the world spirit. For example, he called Napoleon "the world spirit on horseback", because in his view, Napoleon only embodied a part of the world spirit related to war (on horseback), and his historical contribution was essentially a reflection of the world spirit.

Here, Hegel moved towards an idealism (although different from the traditional idealism, his foothold is not material after all). This is also one of the places where Marx criticized his theory. But in the end, Marx found a "communist" export for his materialism theory, and still followed the "positive and negative" system in Hegel's logic to a great extent. Different from Hegel's "absolute spirit", Marx used the concept of "communist society" and put the discussion on a material level. We can also see the far-reaching influence of Hegel's philosophy.