Zhuangzi's great contribution to epistemology is the theory of relativity. He can always see the "treating each other" and the other side of things, subverting the "exclusive" and "self-righteous" thinking. Right and wrong, this and that are always relative, and "this is also right and wrong, and that is also right and wrong" has become a famous saying throughout the ages. He wisely and courageously applied relativity to the concept of life and death, saying that "only when you live can you die, and only when you die can you live". Life and death alternate, just like cold and summer, which is a natural phenomenon, and it is a complete unity of heaven and man in the concept of life and death.