Once, Confucius went to Qi State and saw two children quarreling on the way. One said, "The morning sun is cold and not hot at all; But the sun at noon is as hot as boiling water. Doesn't this mean that the sun is far away from us in the morning and close to us at noon? " The other argued, "No! In the morning, the sun is big and happy, just as big as the canopy on the roof; But by noon, the sun will be smaller, and it will be as big as a dish at most. It is common sense that the near is big and the far is small. " When two children were arguing fiercely, they looked up and saw two adults standing in front of them and asked the elder, "Who are you?" The old man said, "My name is Lu." A child said happily, "Oh, it's Confucius. I hear you are very knowledgeable. Please comment and see who is right. " Confucius honestly admitted: "I can't answer this question. I'll ask someone who has studied angles and answer you later. " The children laughed: "People say Confucius is a saint, and they don't answer questions!" " Confucius looked at the smiling child and said to Lutz, a student around him, "You know what you know in your study, but you don't know what you don't know. Only with this honest attitude can you