It means: the ship is like a monarch, and the water is like Shu Ren. Water can carry a boat and overturn it, which shows that Emperor Taizong attached importance to ordinary people.

"In order to become a monarch, we must first save the people. If you harm the people and serve the people, you will still cut stocks and bite your stomach, which will harm your health. " Therefore, we adopted a series of measures that are conducive to the recovery and development of production and the promotion of social stability, so that the Tang Dynasty was peaceful at home, leaving no roads and not closing households at night. Externally, the national strength is strong and it is attacked on all sides; It was the most powerful feudal country in the world at that time, and it was called "the rule of Zhenguan"

Compare the ship to a monarch and the water to a people. The people can support and oppose the monarch. He is telling himself to care about the people, let them live and work in peace and contentment, and consolidate his rule.