Why?

I was speaking to my dad about things in general and he told me two stories about exam questions that stumped people. One of these questions is a real thinker and that is the one I will tell you now.

A student going for his Masters Degree in Philosophy was writing his final exam one day. He got through all the questions with little trouble and turned to the last page. On the page was written one word. A one word question. Why? Without thinking he wrote down the answer "Why not?"

He received 100% on that answer.

Think about it and comment.