Some people may ask that when the Pythagorean School initially tried to confirm whether √2 is a rational number, they did not know that √2 is not a rational number. In this case, could you ask: √2 can be written in the form of the simplest fraction? The author's answer is: this question is still unreasonable. The reason is that since the arguer does not know whether √2 is a rational number, So, how ensure that this question will not be a complex question? In the case of someone beating his father, there is no logical difficulty in discussing whether he has stopped beating his father. However, when someone has never beaten his father, it is unreasonable to discuss whether he has stopped beating his father, and the situation we face is just similar to the latter.