This is a sentence in Sima Qian's Letter to Ren An. Investigation, research, exploration, discussion and thinking. Heaven, heaven, dharma, nature, destiny, destiny. People, personnel, society, life, dynasty. International, edge, connection, correlation, each other. Pass, straighten out, understand and connect. Change, change, evolution, migration, change.

Summary: Study and explore the unity of opposites between natural law and social law, straighten out and understand the changes and migration from ancient times to the present, and achieve my own independent and perfect theoretical writings.