This was the topic that Yeh Ching-ping, the late chairman of National Taiwan University's Chinese Literature department, assigned to his class. He had asked his students to think seriously about this topic but he was unprepared for their answer.
曾任台大中文系系主任的葉慶炳生前發給學生每人一張紙條，要他們不假思索地寫下答案。