An old black preacher had used the letters B.S., M.S. and Ph.D. after his name for many years without ever having had anyone from his congregation ask what they meant. Finally a nosey old woman questions him about it.
"Well, sister," he answers. "You know what B.S. stands for, don't you?"
"I sure do," says the lady indignantly. "Bull shit!"
"Right," says the preacher. "And M.S. just means more of the same, and Ph.D. means piled high and deep."