This sentence comes from the last chapter of Kant's critique of practical reason, in which Kant first determines the eternal spirit and the existence of God. This book discusses the best problems in life. Kant believes that people should not just look for happiness, but should look for happiness given by God in absolute compliance with moral laws and regulations.
The important theoretical significance of this book lies in that it highlights the problem of human subjectivity, emphasizes the dignity and loftiness of personality, and shows a strong humanistic spirit.
The original sentence is that only the starry sky above the head and the moral law in the heart, the more you think about it, the more you fear it. The whole thing is about rationality, and the principle of thinking existence is considered rationally from the perspective of human beings, especially for the rational existence of human beings.
Every time I open Kant's works, it's like wandering in the Xinghai. Although it is vast and difficult to understand, I can clearly feel that kind of freedom, that kind of freedom that is truly unrestricted by time and space.