For this fascinating trick, David Blaine travels to England, where he performs a mind-reading card trick for the famous physicist Stephen Hawking. He places a deck of cards in front of Hawking and asks him to name any card he wants to. Hawking names 6 of diamonds.
Blaine then reveals that 6 of diamonds is the bottom card of the deck he placed in front of Hawking. Hawking is impressed.
You can see the video of the trick here:
The techique David Blaine used in this trick is called 'multiple outs'. He has many different ways of ending the trick, depending on which card Hawking picked. Maybe if Hawking instead said »6 of hearts«, Blaine would show him that 6 of hearts is at the top of the deck. And if Hawking picked the Ace of Spades, Blaine would say that the Ace of spades is the only card missing from the deck. You get the point.
Whatever card Hawking would pick, Blaine had a separate trick ready especially for that card.