"Doubt is the key to knowledge" (Persian Proverb)

I think this Persian Proverb is absolutely right. Doubt is the key to knowledge because everytime that you doubt something you start looking for the real answer and you discover new things, hence you get more knowledge.

1. In history, for example, if there is a certain event that you doubt that it really happened you search for it and you look for what really happened. Therefore, you have more knowledge on what really happened on that event.

2.In school, for example, in my math class I have certain doubts about the formulas, so I question Mr. McDowell and he tells me the real answer.

3.Once my car had mechanical problems so I took it to an auto-mechanic shop and they told me that the radiator was giving the car problems. I doubted it was the radiator, and the next day the car still gave me problems so I took it again to the workshop and it turned out it was the engine.