To clarify this, (1) means the empty door, as revealed, was not picked from a random set of doors with anything or nothing behind them. Rather, (1) and the link

To clarify this, (1) means the empty door, as revealed, was not picked from a random set of doors with anything or nothing behind them. Rather, (1) and the link, both refer to a case where the game show host picks a random door only from doors known to be empty, presumably to raise the tension in the show. (Opening the door with something behind it would eliminate the tension, after all.) I also like the answers later in the HN comments where someone mentions the host opening a bunch of empty doors, leaving one closed, then asking if you'd like to switch to the door he or she conveniently left closed.