I had read a story, in which a professor argues that there is no existence of God as there is no proof of his presence and he is ready to believe if somebody shows the God in front of him.
Then a student started his version. "Does any one of this class has seen our professor's brain? The answer is certainly 'No'. So, does it mean that he don't have brain"
(I also heard that the student is our honourable president A.P.J. Abdul Kalam (For the post of president there is no Former))