Encouraging officials to give advice, being willing to accept advice, having the courage to make corrections, and truly doing good things. This is not only the biggest highlight of Tang Taizong, but also the foundation of his life's virtues. Without this, he would At best, he is just a successful founding monarch like Han Gaozu Liu Bang, Guangwu Emperor Liu Xiu, Song Taizu Zhao Kuangyin and others. After the death of Wei Zheng, a famous minister of the Tang Dynasty, Emperor Taizong of the Tang Dynasty mourned him and said: "People use copper as a mirror to correct their clothes and hats; people use ancient times as a mirror to see the ups and downs of gains and losses; people use people as a mirror to know gains and losses; Wei Zheng died "I am dead in a mirror." This is a famous saying that has been widely recited by later generations, but there is an inaccuracy here. Emperor Taizong of the Tang Dynasty did not use Wei Zheng as a mirror to observe his own gains and losses. The mirror he used for reference was actually Sui Yang. Emperor Yang Guang. Wei Zheng was just a good supervisor with extremely accurate eyesight and the courage to correct Taizong's mistakes.