Of course you don't know. You don't know because only *I* know. If you knew and I didn't know, then you'd be teaching me instead of me teaching you - and for a student to be teaching his teacher is presumptuous and rude. Do I make myself clear?
Charlie Bucket: Hey, the room is getting smaller. Mrs. Teevee: No, it's not. *He's* getting *bigger*! Mr. Salt: He's at it again! Mike Teevee: Where's the chocolate? Sam Beauregarde: I doubt if there is any. Mr. Salt: I doubt if any of us will get out of here alive. Willy Wonka: Oh, you should never, never doubt what nobody is sure about. Mrs. Gloop: You're not squeezing me through that tiny door! Mr. Salt: You're off your bleeding nut, Wonka. No one can get through there!