The meaning of this passage of Confucius is: teach students not to enlighten them until they think hard and can't figure it out, so that they are anxious, depressed and even miserable; Tell him (a square object) that one corner can't bypass the other three corners by analogy, so he won't be taught more and deeper knowledge. This is the origin of the idiom "draw inferences from one instance to another". People can see that Confucius' thoughts and methods of grasping the opportunity, guiding the situation and proceeding step by step are very different from today's cramming teaching.