This sentence is a famous saying of the great German philosopher Immanuel Kant. It was originally published in the book "Critique of Pure Reason". Later, after Kant's death, this sentence became his epitaph.

This passage from Kant is extremely wonderful and can be said to be a refined expression of his philosophical contribution. Here, factual cognition and moral cognition finally find a connection, that is, human reason. Behind the starry sky above and the moral laws in the heart, human reason provides support.

In Kant's view, people are in two worlds at the same time, one is the real world and the other is the value world, as Kant said in "Principles of the Metaphysics of Morals":

As far as it is only perception, as far as the susceptibility of sense is concerned, man belongs to the sensory world and reaches consciousness directly without going through sense. As far as his pure initiative is concerned, man belongs to the intellectual world. We don't know much about this world yet.

The reason why people can have moral cognition and the awareness of "should" is precisely because people are in these two worlds at the same time:

"Therefore, the categorization The reason why command is possible is that the concept of freedom makes me a member of the Intelligent Welt. If I are only a member of this world, then all my actions will always be consistent with the autonomy of the will. However, since I am a member of the sensory world at the same time, I should conform to this law.

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