A college class was led by an atheist professor, and every day he'd stand in front of his class and say, "Have you ever seen God?" to which nobody would answer. Then he'd ask, "Have you ever felt God?" and nobody would answer. Finally he'd ask, "Have you ever heard God?" and, like the other times, nobody would answer. He then would say, "It is obvious that there is no God."
One day a Christian student had been having an extremely bad day; her car broke down, her mother was sick, her boyfriend was out of town, and she'd gotten a bad grade on one of her exams. She had been fed up with her professor's little act every morning, so she decided to do something about it.
While the professor stood up at the beginning of class and did his thing, the student had an idea. She got up and said, "Professor, would you mind if I said something?" He said, "Of course not. This is an expressive classroom, and I think it would be fine if you spoke your mind."
The girl said to the class, "Have you ever seen our professor's brain?" and nobody answered. Then she asked, "Have you ever felt our professor's brain?" and nobody answered. Finally she asked, "Have you ever heard our professor's brain?" and, like the other times, nobody answered.
She then said, "It is quite obvious that our professor has no brain."