Emperor Taizong's famous saying, "You can know gains and losses", in which ""generally refers to the experience and lessons of people's success or failure. Confucius' famous words in the Analects of Confucius. The "virtuous" and "not virtuous" here refer to people's ability level. Another famous saying of Confucius in The Analects of Confucius. The "good guys" and "bad guys" here refer to the quality of people's foundation. It is precisely because people's success or failure is related to their own ability level and their own advantages and disadvantages, so the famous saying of Emperor Taizong "knowing gains and losses" can be completely reconciled with the famous saying of Confucius in The Analects of Confucius "Look at the sages, look at them and reflect on them more". Emperor Taizong commented on Wei Zhi's "Biography of Old Tang Books and Wei Zhi": "A husband can take a bronze coat as a mirror; Taking history as a mirror, we can know the rise and fall; Taking people as a mirror can give you a glimpse of gains and losses. "