Kant's era is an era in which empiricism and rationalism argue with each other. Empiricism is the philosophy of "being is perception" and "there is no causal relationship, only the order of perception", which holds that knowledge comes from sensory perception and is the only source of knowledge. The representative figures of empiricism are Hobbes, Locke, Becquerel and Hume. The representatives of rationalism are Bacon and Spinoza. Kant is a synthesis of empiricism and rationalism. This characteristic of Kant has been reflected from the very beginning of pure rational criticism.

He believes that knowledge can be divided into two kinds, one is empirical and the other is innate. Empirical knowledge is knowledge derived from sensory perception, which can only be obtained through sensory perception. Knowledge that belongs to this category, such as topography, mountains and rivers, observation in astronomy and morphology in biology, also belongs to empirical knowledge. An important feature of empirical knowledge is the expansion and naming of perception. For example, telescopes and microscopes, as well as various types of detectors, are expanding the range of human perception. With the expansion of the scope of perception, new empirical knowledge has emerged. Electron microscope enables us to deeply observe the internal structure of cells, even directly observe molecules and atoms; Large-aperture and high-precision telescopes enable us to observe galaxies billions of light years away and recognize the interaction at the galaxy level.

What kind of knowledge comes from experience is not enough?

Lack of experience means that this knowledge has experience participation, but it must also have non-experience participation. For example, the blackbody radiation problem encountered in the laboratory and the photoelectric effect are all part of the experience. Experience can never get the laws of quantum mechanics from these two experiments. Quantum mechanics was put forward to explain these two experiments, so where did the discovery of quantum mechanics come from? It is impossible for anyone to gain such profound knowledge only by sensory perception experience. Can you put forward non-Euclidean geometry by seeing the triangle on the sphere through sensory perception? Even Euclidean geometry can be put forward by perceiving one triangle after another? Can you simply observe the changes of things and finally summarize the mathematical equations describing the changes? The space-time view of relativity is not felt by sensory perception at all, and it obviously cannot be put forward only by experience. Parallel world is the solution of physical equation, which is not felt by human sensory perception. These are all innate knowledge. Although all this knowledge is accumulated by experience, it is later than experience in time, but as far as their establishment is concerned, it was established before experience.

Won't the earth not revolve around the sun because the ancients didn't know it? Will the law of gravity fail because people don't know it? Can electrons become particles because the wave-particle duality is unknown? The existence of innate knowledge precedes experience and is transcendental knowledge. The discovery of this kind of knowledge needs the participation of the ability beyond experience and the power beyond experience. The ability to transcend experience is the ability to acquire knowledge beyond sensory perception.

Knowledge without any experience is pure knowledge, that is, knowledge without any sensory perception. Xinjiang has Tarim basin, which is purely empirical knowledge. This is a description of this phenomenon. The greater the force that drags an object, the faster it runs. This is innate knowledge including experience, and both strength and speed are perceptual knowledge. Reason is the best, neither reason nor best is perceptual knowledge, and the best of reason cannot be obtained through experience, which is pure knowledge.

For example, "all changes must have their reasons", Hume thinks this is an empirical understanding, that is, an event must happen after an event. Kant's refutation of Hume is inevitable, and knowledge cannot be obtained from accidental experience. The contingency of experience, for example, water may or may not freeze at 0℃ in experience, even pure water is exactly the same, and we can't completely guarantee that experience must be that water will freeze at 0℃. Because the representation of experience has been changing before, how can we think that the representation of experience must be inevitable because all factors are consistent? Therefore, experience itself cannot provide the inevitability of knowledge. Therefore, an event must happen after an event, which is beyond experience. Similarly, experience is limited. Just because we have pain and the people around us have pain, we can't conclude that everyone has pain. Just because we observe that Mercury, Venus, Earth and Mars are all rotating vertically, we can't think that all the planets are rotating vertically. Experience cannot bring universal applicability. Experience can only prove that some changes have reasons, but not all changes have reasons. Popularization from local to universal is not a task that experience can accomplish.

Not all generalizations from local to universal are inherently effective. For example, from a few apples are sweet to all apples are sweet, which is not born. It is a generalization of empiricism, which only arbitrarily extends local effectiveness to universal effectiveness. Only when universality is a kind of judgment in essence, this universality comes from innate knowledge ability, which we call strict universality. What is essential judgment? For example, the proposition "Everything has a cause" is not an empirical generalization, but an abstract generalization, and we can judge this proposition without experience. So it is essentially a judgment, that is to say, this proposition can be judged whether it is true or not without relying on experience, and this judgment is absolutely correct. "All apples are sweet", to judge the truth of this proposition, we must experience all apples, otherwise this proposition can never be absolutely true, and there are always exceptions if rotten apples are not sweet; Another example is the proposition that "all birds can fly", which is an empirical generalization, so there will be exceptions. Experience popularization often encounters exceptions, while the universality of innate knowledge and ability is absolute, without exceptions.