The knife cuts bread and fingers. Li Shimin, Emperor Taizong of Tang Dynasty, established a peaceful and prosperous period of "the rule of Zhenguan", and knowing people and being good at their duties was one of the conditions for success. When discussing the strategy of governing the country, Wei Zheng and Taizong, the famous ministers, put forward the wise conclusion that "water can carry a boat, but it can also overturn it", and expounded the profound truth of governing the country and safeguarding the country. "Water can carry a boat, but it can also overturn it." The water here refers to "people" and the boat here refers to "imperial power". That is, the people can maintain the feudal regime, but also overthrow the feudal regime, whether the key rulers comply with public opinion and win the hearts of the people. "Don't forget the past, the teacher of the future." Looking back at history, we can get a lot of useful things from the rise and fall of feudal dynasties in history. Ying Zheng, the first Qin Emperor, was a very talented historical figure who fought the sword, destroyed six countries, swallowed up eight famine and established the Qin Dynasty. After the establishment of the Qin Dynasty, they did not know how to cultivate and develop production, but pursued tyranny, built houses, built the Great Wall, burned books and buried Confucianism, and made the disabled show off, causing widespread indignation and resentment. Shoujiang Chen Sheng and Guangwu climbed high, and the world responded. The Qin Dynasty soon collapsed and became a powerful and short-lived dynasty in the history of China. (Ying Zheng reigned for 27 years, while his son Qin Ershi Hu Hai reigned for only 3 years. The experience and lessons here are profound. The demise of the Qin Dynasty was the result of his tyranny and the great victory of the people against tyranny.