Kant is a link in the historical chain of Western philosophy, and an indispensable link in the continuation of the past and the future.
"Inheriting the former" is that he is to untie the dead knot that Hume put on empiricism and rationalism; "Enlightenment" is the first for him to start the surging development of German classical philosophy.
As we all know, modern Western philosophy began with Descartes. This mathematician and philosopher established the edifice of the first philosophical system in modern Times in the West, and also pointed out two paths for the development of philosophy for future generations - empiricism and rationalism.
If the characteristics of these "two isms" are described in the words "simplest", then empiricism focuses on exploring how knowledge is reliable; rationalism studies the boundaries of man's cognitive ability. Naturally, any "division" is relative; nor can all "descriptions" be completely precise. However, in modern Western philosophy, it has always taken "how is knowledge reliable" and "where are the boundaries of cognition" as the core topics, which is the basic consensus.
But by Hume, it seemed as if both doctrines had come to an end.
David Hume
He started with empiricism. He argues for the unprovable and unreliability of "causality.". Without a solution to the problem, he said, any knowledge is questionable. This not only embarrasses empiricism, but also rationalism—is man's cognitive faculties reliable?
Prior to this, Kant was enthusiastic about studying science and published several papers, for example, on the nebula hypothesis. His approach is not based on a large number of experimental observations, as the average scientist does, but more of a philosophical reflection, but it is also profound enough. But after reading Hume's philosophy, Kant exclaimed, and Hume woke him up from his sleep. Thus, a quick turn was made to "metaphysics", that is, purely philosophical thinking.
The problem facing Kant was the need to "limit Hume's skepticism on the one hand, and arbitrariness on the other." He still had to answer the two questions mentioned earlier.
Kant's philosophy also begins with "what is knowledge" and "how is knowledge reliable". The difference is that he begins to expound from the perspective of "human reason" that rationalism excels at. Knowledge, he said, always takes the form of judgment, in which there is some affirmation or negation. However, not every judgment is knowledge.
The above statement is almost the same as Hume's. Obviously, Kant meant to start from Hume and come to very different conclusions.
Immanuel Kant
Kant said that certain knowledge from experience lacks universality and inevitability and cannot be regarded as knowledge. Judgments that lack universality and necessity or "posterior" judgments are unscientific. Without relying on experience, and in this sense "preceding experience", for example, the sum of the three inner angles of a triangle is equal to two right angles, and always so, this is knowledge. Therefore, for a judgment to give knowledge, it must be "a priori".
With regard to "a priori", Kant divided it into "a priori sensibility" and "a priori logic".
"A priori sensibility" means that to be perceptual, there must be sensations, such as feeling color, sound, hardness, and so on. But there is only sensation, not knowledge, only a change in consciousness, only a subjective state in which something else produces man. Sensation must involve space-time, a certain place in space-time; sensation must be understood as something external—next to something; before or after something. People's feelings are arranged in the order of time and space.
Thus, perception, with material or content (sensation) and (form) as necessary conditions—space-time—is a necessary "form" condition of perception.
Feeling is the first step, perception is the second step. The mind not only receives sensations, but also "perceives" the sensations—seeing colors, hearing sounds outside of it, in the order of time and space. Sensibility, with the ability to perceive space and time "a priori"—it can perceive space-time even when no objects are presented; it can perceive not only objects in space-time, but also space-time itself.
Kant repeatedly emphasized that the arrangement of sensations in space-time, the form or form itself, is not the sensation. For this ability is not empirical or "a posterio" but inherent in the nature of the mind, that is, "a priori."
He further analyzed that space-time is not real, or something that exists alone, nor is it the nature and relationship of things themselves. He said that space-time is the way in which the senses understand things, the form or form of the senses. If there are no people in this world who can intuitively or perceive space-time, the world no longer has the nature of space and time.
He said: "Let the subject of thinking leave, and the whole material world will disappear, because this material world is nothing more than a phenomenon felt by the subject of thinking." This sentence is like Both Descartes and Berkeley, and somewhat like Hume.
Kant repeatedly remembered that space-time is merely a condition of the senses, or rather, the form of sensory perception, i.e., the way in which human beings perceive things. Therefore, they are effective only when they are used for perceived things, that is, phenomena, and not for "things in themselves" or things that are independent of human perception.
In the above sense, it is "a priori sensibility". Kant goes on to discuss "a priori logic," which will not be repeated here.
Hegel said: "Space and time are also connectors; therefore they are also innate, i.e., within self-consciousness." This is the great side of Kant's philosophy. ...... But, on the other hand, his play on this idea remains within a very ordinary, crude, empirical point of view, and cannot be said to be scientific."
Georg Wilhelm Friedrich Hegel
Hegel's so-called great side of Kant's philosophy refers to Kant's breakthrough in Hume's philosophy, or at least an attempt to break through. However, he pointed out that Kant's view of "a priori", including the "a priori" of space-time, "cannot be said to be scientific", should hit Kant's point.
Hegel said: "As for why the mind happens to have these forms, what is the nature of time and space, Kant's philosophy does not ask at all. When he talks about what space and time itself are, he doesn't ask: What are their concepts? But just ask: Are they external things, or are they something inside the mind? This can't help but remind people of a Chinese idiom called "yuanmu for fish.".
It is undeniable that Hegel's philosophy was deeply inspired by Kant's philosophy. And this inspiration is likely to come from his dissatisfaction with Kant's philosophy of "shallow taste".
Hegel said: "In fact, we see that Kant is describing only an empirical, limited sense of self, which requires a material external to it (such as the form of space-time), in other words, a separate, limited self-consciousness. ...... So what we know and what we prescribe is only a phenomenon. Kant's philosophy in this sense is called idealism: we are merely dealing with our rules, we cannot attain self-existence; we cannot attain true objective things (i.e., we cannot attain essential knowledge)."
Indeed, Hegel's philosophy is much deeper than Kant's; the logic is much more rigorous; the system is much larger. But in any case, Hegel developed from this ring of Kant's philosophy.