# Where truths meet lies

Popular Science - - TALES FROM THE FIELD - by Claire Mal­darelli

QUES­TION ONE:

This party of lo­cals is made up of two classes of peo­ple: war­riors and lords. They are as much dif­fer­ent as they are the same. The cru­cial thing you need to know about them is that war­riors al­ways tell the truth, and lords al­ways lie. There are no ex­cep­tions to this rule.

Two peo­ple stand guard next to each other, watch­ing the area. One wears green and the other red. A sign tells you that you can pass if you can cor­rectly iden­tify which type of cit­i­zen each of them is: Are they a war­rior or a lord?

The one in green says: “There’s at least one lord stand­ing be­fore you.” Sim­ple enough, but you can glean much in­for­ma­tion from that sen­tence. What type of is­landers are they?

QUES­TION TWO:

You an­swer cor­rectly and con­tinue your trek. Soon, you reach a fork in the road and an­other pair of lo­cals stand­ing guard, waiting for you to ar­rive.

This time, you know for sure that one of them is a lord and one is a war­rior. And, as luck would have it, they know where your ho­tel is. How­ever, you don’t know which is which. To find out which di­rec­tion leads you back to your res­i­dence, you are al­lot­ted just one ques­tion for them to an­swer. What ques­tion do you ask? (Hint: De­cide on a query that both a war­rior and a lord would have to pro­vide the same an­swer to.)

ques­tion one: Green is a war­rior, red is a lord. This re­mains true if the one in green is a war­rior or a lord. But, if green were a lord, they’d be ly­ing. So, green can only be a war­rior, mak­ing red a lord. ques­tion two: Which di­rec­tion would the other per­son tell me to go to get me in the right place? If the per­son you ask is a war­rior, the other must be a lord. The lord would lie and say the op­po­site of where to go. If the per­son were a lord, the other would be a war­rior bear­ing the truth—but the lord would lie about what the war­rior says. In ei­ther case, you would get the op­po­site of the cor­rect di­rec­tion.