The first theory: This sentence was engraved on the stone pillars of the Temple of Apollo in ancient Greece. Later proposed by the famous philosopher Socrates.

The second theory: comes from Greek mythology. There is this saying in Ovid's "Kama Sutra": Apollo said: "Bring your disciples to my temple quickly, where they can recite the world-famous inscription: Mortal, know thyself."

Understanding: Knowing yourself represents the attitude that people should have in terms of knowledge. Instead of understanding the world, it is better to understand more about yourself, because people can never understand the world enough, and they can never stop, only themselves. It is most relevant to everyone.