In the late World War II, American President Roosevelt put forward the slogan of "Four Freedoms", namely "freedom of speech, freedom of belief, freedom from want and freedom from fear". Yan, a civilian educator in China, made a supplement to this. He said: "We can't have only four freedoms, but also a fifth freedom, which is great compared with the other four. Without it, can we have the "four freedoms"? This is freedom from ignorance. "