A freshman in college started his first day of classes.
His philosophy professor was clearly an atheist, and started the day by saying the following:
"Students, is there anyone here who can see God? If so, raise your hand.
If there is anyone here who can hear God, raise your hand.
If there is anyone who can smell God, raise your hand."
After a short pause, with no response from the students, he concluded,
"Since no one can see, smell or hear God, there is no God."
A student then raised his hand and asked to address the class.
The student approached the class and asked,
"Students, can anyone here see the professor's brain?
Can anyone hear or smell the professor's brain?"
After a short pause, he concluded, "Since no one else can see, hear or smell the professor's brain,
I conclude that he has no brain!"