Knowlege

A girl asked a psychiatrist:

Doctor, how to know whether a person, whose appearance is completety normal, has problems or not?

Very easy-the doctor answered-Ask that person a simple question which can be answered easily. If he can't answered of splutter, it means he has mental problems. 

What question, for example?-the girl was curious-can you make a try on me?

For example: Capital Cook went around the world three time and he died in one of these three time. In which of these three time did he died?

The girl thought for a few minutes and said with a worried smile:

Could you ask me an other question? I think I don't know much about history