There was a time in Kant's life when the most skeptical argument was painful. At that time, he wrote a wonderful book called Ghost Catcher's Dream (taking Dream of Metaphysics as an example) (1766). The "soul prophet" is Pauli of Sweden. His mysticism system was made public with a great book. Four copies of this book were sold, three of which were bought by unknown buyers, and 1 was sold to Kant. Kant called Sweden's Bao Li system an "absurd" system; He said, half seriously and half jokingly, that Bao Li system in Sweden is no weirder than orthodox metaphysics. However, he doesn't completely despise Swede Pauli. His mysticism exists, although it is not shown in his works; His side praised Swede Pauli, saying that he was "very noble".

Like everyone around him at that time, he wrote a paper on sublimity and beauty. The night is noble and the day is beautiful; The sea is lofty and the land is beautiful; Men are noble and women are beautiful; And so on.

The Encyclopedia Britannica said: "Because he has never been married, he kept the habit of eager to learn from his youth until his old age." I wonder if the author of this article is single or married.

Kant's most important book is Critique of Pure Reason (first edition, 178 1 year; Second edition, 1787). The purpose of this book is to prove that although there is nothing beyond experience in our knowledge, some of it is still innate rather than inferred from experience in an inductive way. Our knowledge is an innate part. According to him, it not only contains logic, but also contains many things that cannot be classified or deduced from logic. He divided Leibniz into two types. On the one hand, there is a difference between "analysis" and "synthesis"; On the other hand, there is a difference between "innate" proposition and "experience" proposition. Regarding these two differences, we need to say our own.

The proposition of "analysis" is that the predicate is part of the subject; For example, "tall people are people" or "equilateral triangles are triangles". This proposition is the conclusion of the law of contradiction; It is contradictory to think that tall people are not people. The "comprehensive" proposition is not an analytical proposition. All the propositions we know through experience are comprehensive propositions. For example, only analyzing the concept, we can't find the truth that "Tuesday is rainy" and "Napoleon is a great general".

But Kant, unlike Leibniz and all philosophers before him, does not recognize the opposite, that is, a comprehensive proposition can only be known through experience. This brings us to the second of the above two differences.

The proposition of "experience" is a proposition that we can't know except by means of sensory perception, or our own sensory perception, or other people's sensory perception, which we admit to prove. Historical and geographical facts belong to this category; Whenever our understanding of the truth of scientific laws depends on observation data, scientific laws also belong to this category. Conversely, the "innate" proposition is such a proposition: although it can be drawn from experience, once it is known, it will be seen that it has other foundations besides experience. When a child learns arithmetic, he experiences two pebbles and two others. Observing that he has been experiencing four pebbles can help him learn. But when he understood the general proposition that "two plus two equals four", he no longer needed to prove it with examples; This life problem has a kind of induction, which can never give certainty to the general law. All propositions in pure mathematics are innate propositions in this sense.