The student explained. "I learned in University that all things are the way they are because that is how I perceive them. Everything exists to me only because I have a vague and inaccurate image of it in my mind. And, really... if I can't even believe in you or your desk or the soil in my yard... how can I possibly believe in something as abstract as God?"
"So," the Rabbi says, "you can't even really know that, say, your own nose exists?"
"Exactly!" the student answered. "Not even my own nose."
The Rabbi pauses thoughtfully, rubbing his chin. After a moment, the Rabbi turns to the student and punches him. Hard. In the nose.
The Rabbi then leans over the student, crumpled on the ground, holding his bloody nose and moaning.
"So, my boy," the Rabbi says, "what hurts?"
