YOU SIT DOWN AT A TABLE AND THE A MAN. HE INTRODUCES HIMSELF, LIGHTS HIS PIPE, THEN LAYS FOUR CARDS DOWN CAREFULLY IN FRONT OF YOU. THE FIRST CARD SHOWS THE NUMBER FIVE, AND THE SECOND CARD SHOWS THE NUMBER EIGHT. THE THIRD CARD IS BLUE, AND THE FOURTH CARD GREEN. THE MAN LOOKS AT YOU, AND SAYS:
“IF THERE IS AN EVEN NUMBER ON ONE SIDE OF A CARD,” HE SAYS, “THEN THE OPPOSITE SIDE IS ALWAYS BLUE.”; HERE’S THE THING: HE’S PROBABLY LYING. YOU KNOW THIS, BUT NOW YOU HAVE TO PROVE IT. WITHOUT TURNING ANY UNNECESSARY CARDS, WHICH CARDS ON THE TABLE WOULD YOU HAVE TO FLIP OVER IN ORDER TO PROVE WHETHER THE MAN’S STATEMENT IS TRUE OR FALSE?