a clairvoyant being presents you with two boxes: one is open, and has $1000 in it. The other one is closed, and you're told it contains either nothing or $1,000,000.
The being asks you to choose to take either both boxes, or just the closed one. He claims (due to his clairvoyance) that if he predicted you would choose the closed one, then he put the $1,000,000 in it. If he predicted you would choose both, he left it empty.
The paradox is: which do you choose? Both, or just the closed box? Why?
(Link to essay by Franz Kiekeben)