For education, the most difficult thing to change is not ignorant people, but knowledgeable people, especially knowledgeable people. People with high knowledge, because they get too much knowledge, will subconsciously have an illusion that I know. I know this, so that I can't devote myself to learning some knowledge outside the field. Everything I have learned floats on the surface of my mind, only knowing one thing and not knowing the other. I know the surface, but I can't understand the essence.