In a perfect world, chickens could cross the road without having their motivations questioned. But this isn’t a perfect world, and human beings are imperfect creatures. Hence people keep asking, “Why did the chicken cross the road?”

Yet what possible difference could it make, why an anonymous chicken crossed some unnamed road? Sherlock Holmes, in The Sign of Four, suggests a potential answer: “I cannot live without brain-work. What else is there to live for?”

And thus there are many books of riddles, but this isn’t one of them. What we have here is an intellectual party game—Explain This!—based on lateral thinking puzzles. (Details and rules are found below.) The game, which originated as an academic teaching tool during the 1960s, is designed to be fun for smart people. This book is written with the hope of being likewise amusing.

Brainteasers often take a generic form. The most dreaded variety starts out, “If a train leaves St. Louis traveling 60 miles per hour…,” at which point most people blurt back, “…how far is it to the bar car?”

Parties are fun. Games are fun. Why else would we engage in them? (We could, after all, just sit around worrying.) Combine the two and we end up with the fortuitous equation: parties + games = fun x 2.

“My mind,” said Holmes, “rebels at stagnation. Give me problems, give me work, give me the most abstruse cryptogram or the most intricate analysis, and I am in my own proper atmosphere.” Lots of people, though, prefer a more festive atmosphere.

The first party game that many of us remember, for reasons that require little explanation, is Spin the Bottle. One kid randomly kissing another kid while other kids look on. Then comes Post Office, where half the kids kiss all the kids in the other half (typically split by gender), after which the kissers and kissees switch roles. Unless the kids play in complete darkness (a more daring version called Pony Express), other kids look on.

Some adults eventually move on to “key parties,” where half of the attendees (typically all the men or  women) drop their car keys into a bowl. At some point, depending one imagines on the “temperature” in the room, the second group draws keys at random and heads home with their particular “designated driver.” At least in the end they don’t make others look on. Perhaps they show the video later.

Easy [ – – 3 – -] Hard

A man reads in the paper that Mr. Smith and his wife were skiing in the Alps, and that Mrs. Smith had an accident, fell off the mountain, and was killed. The man puts down the paper and calls the police. “That was no accident,” he says, “Mr. Smith killed his wife.”

Explain this!

Easy [ – – – 4 -] Hard

Two women enter a bar and order the same exact drink. One finishes the drink quickly, then leaves without consequences. The other nurses the drink and dies within a couple of hours.

Explain this!