The purpose of anticipatory demonstration is to grasp the purpose. The positive and negative examples are compared. In the first half, the author explained the reality that the society was keen on being an official at that time with shocking examples, and analyzed the situation that Peking University paid attention to fame and fortune instead of academics at that time. In the part of "purpose established, we are on the right track", two different results of learning and not learning are demonstrated by positive and negative comparison. The author of "The Theory of Honing Virtue" first puts forward a sub-argument, arguing that customs are crucial to the rise and fall of a country, and then puts forward another argument, affirming that college students are "excellent people" who will be honest and clean, and will not be infected by customs, and then asking them to set an example and try their best to correct them. There is a reasoning process. For example, treat teachers and friends sincerely from the perspective that teachers and staff are committed to facilitating students' learning; From the perspective of students living together, they should be dear to each other; Then give an example to show that ordinary people praise each other, and teachers and students should encourage more.