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- From: uunet!questrel!chris (Chris Cole)
- Subject: rec.puzzles FAQ, part 13 of 15
- Message-ID: <puzzles-faq-13_717034101@questrel.com>
- Followup-To: rec.puzzles
- Summary: This posting contains a list of
- Frequently Asked Questions (and their answers).
- It should be read by anyone who wishes to
- post to the rec.puzzles newsgroup.
- Sender: chris@questrel.com (Chris Cole)
- Reply-To: uunet!questrel!faql-comment
- Organization: Questrel, Inc.
- References: <puzzles-faq-1_717034101@questrel.com>
- Date: Mon, 21 Sep 1992 00:09:46 GMT
- Approved: news-answers-request@MIT.Edu
- Expires: Sat, 3 Apr 1993 00:08:21 GMT
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-
- Archive-name: puzzles-faq/part13
- Last-modified: 1992/09/20
- Version: 3
-
- ==> logic/situation.puzzles.s <==
- Answers to Jed's List of Situation Puzzles
-
- This is the list of answers to the puzzles in my situation puzzles
- list. See that list for more details. This document also contains
- variant setups and answers for some of the puzzles.
-
- Section 1: "Realistic" situation puzzles.
-
- 1.1. A bunch of people are on an ocean voyage in a yacht. One afternoon,
- they all decide to go swimming, so they put on swimsuits and dive off the
- side into the water. Unfortunately, they forget to set up a ladder on the
- side of the boat, so there's no way for them to climb back in, and they
- drown.
- 1.1a. Variant answer: The same situation, except that they set out a
- ladder which is just barely long enough. When they all dive into the
- water, the boat, without their weight, rises in the water until the ladder
- is just barely out of reach. (also from Steve Jacquot)
-
- 1.2. The room is the ballroom of an ocean liner which sank some time ago.
- The man ran out of air while diving in the wreck.
- 1.2a. Variant which puts this in section 2: same statement, ending with
- "a large window through which rays are coming." Answer: the rays are
- manta rays (this version tends to make people assume vampires are
- involved, unless they notice the awkwardness of the phrase involving
- rays).
-
- 1.3. The husband killed himself a while ago; it's his ashes in an urn on
- the mantelpiece that the wife looks at. It's debatable whether this
- belongs in section 2 for double meanings.
-
- 1.4. A poor peasant from somewhere in Europe wants desperately to get to
- the U.S. Not having money for airfare, he stows away in the landing gear
- compartment of a jet. He dies of hypothermia in mid-flight, and falls out
- when the landing gear compartment opens as the plane makes its final
- approach.
- 1.4a. Variant: A man is lying drowned in a dead forest. Answer: He's
- scuba diving when a firefighting plane lands nearby and fills its tanks
- with water, sucking him in with the water. He runs out of air while the
- plane is in flight; the plane then dumps its load of water, with him in
- it, onto a burning forest. (from Jim Moskowitz)
-
- 1.5. The man is a midget. He can't reach the upper elevator buttons, but
- he can ask people to push them for him. He can also push them with his
- umbrella. I've usually heard this stated with more details: "Every
- morning he wakes up, gets dressed, eats, goes to the elevator..." Ron
- Carter suggests a nice red herring: the man lives on the 13th floor of the
- building.
-
- 1.6. The sisters are Siamese twins.
- 1.6a. Variant: A man and his brother are in a bar drinking. They begin to
- argue (as always) and the brother won't get out of the man's face, shouting
- and cursing. The man, finally fed up, pulls out a pistol and blows his
- brother's brains out. He sits down to die. Answer: They are Siamese twins.
- In the original story, the argument started when one complained about the
- other's bad hygiene and bad breath. The shooter bled to death (from his
- brother's wounds) by the time the police arrived. (from Randy Whitaker,
- based on a 1987 _Weekly World News_ story)
-
- 1.7. The man has hiccups; the bartender scares them away by pulling a
- gun.
-
- 1.8. The man used to be blind; he's now returning from an eye operation
- which restored his sight. He's spent all his money on the operation, so
- when the train (which has no internal lighting) goes through a tunnel he
- at first thinks he's gone blind again and almost decides to kill himself.
- Fortunately, the light of the cigarettes people are smoking convinces him
- that he can still see.
- 1.8a. Variant: A man dies on a train he does not ordinarily catch.
- Answer: The man (a successful artist) has had an accident in which he
- injured his eyes. His head is bandaged and he has been warned not to
- remove the bandages under any circumstances lest the condition be
- irreversibly aggravated. He catches the train home from the hospital and
- cannot resist peeking. Seeing nothing at all (the same train-in-tunnel
- situation as above obtains, but without the glowing cigarettes this time),
- he assumes he is blinded and kills himself in grief. I like this version
- a lot, except that it makes much less sense that he'd be traveling alone.
- (from Bernd Wechner)
-
- 1.9. The man was in a ship that was wrecked on a desert island. When
- there was no food left, another passenger brought what he said was abalone
- but was really part of the man's wife (who had died in the wreck). The
- man suspects something fishy, so when they finally return to civilization,
- he orders abalone, realizes that what he ate before was his wife, and
- kills himself.
- 1.9a. Variant: same problem statement but with albatross instead of
- abalone. Answer: In this version, the man was in a lifeboat, with his
- wife, who died. He hallucinated an albatross landing in the boat which he
- caught and killed and ate; he thought that his wife had been washed
- overboard. When he actually eats albatross, he discovers that he had
- actually eaten his wife.
- 1.9b. Variant answer to 1.9a, with a slightly different problem
- statement: the man already knew that he had been eating human flesh. He
- asks the waiter in the restaurant what kind of soup is available, and the
- waiter responds, "Albatross soup." Thinking that "albatross soup" means
- "human soup," and sickened by the thought of such a society (place in a
- foreign country if necessary), he kills himself. (from Mike Neergaard)
-
- 1.10. He stood on a block of ice to hang himself. The fact that there's
- no furniture in the room can be added to the statement, but if it's
- mentioned in conjunction with the puddle of water the answer tends to be
- guessed more easily.
-
- 1.11. He stabbed himself with an icicle.
-
- 1.12. He jumped out of an airplane, but his parachute failed to open.
- Minor variant wording (from Joe Kincaid): he's on a mountain trail instead
- of in a desert. Minor variant wording (from Mike Reymond): he's got a
- ring in his hand (it came off of the ripcord).
- 1.12a. Silly variant: same problem statement, with the addition that one
- of the man's shoelaces is untied. Answer: He pulled his shoelace instead
- of the ripcord.
- 1.12b. Variant answer: The man was let loose in the desert with a pack
- full of poisoned food. He knows it's poisoned, and doesn't eat it -- he
- dies of hunger. (from Mike Neergaard)
-
- 1.13. He was with several others in a hot air balloon crossing the
- desert. The balloon was punctured and they began to lose altitude. They
- tossed all their non-essentials overboard, then their clothing and food,
- but were still going to crash in the middle of the desert. Finally, they
- drew matches to see who would jump over the side and save the others; this
- man lost. Minor variant wording: add that the man is nude.
-
- 1.14. The radio program is one of the call-up-somebody-and-ask-them-a-
- question contest shows; the announcer gives the phone number of the man's
- bedroom phone as the number he's calling, and a male voice answers. It's
- been suggested that such shows don't usually give the phone number being
- called; so instead the wife's name could be given as who's being called,
- and there could be appropriate background sounds when the other man
- answers the phone.
-
- 1.15. He worked as a DJ at a radio station. He decided to kill his wife,
- and so he put on a long record and quickly drove home and killed her,
- figuring he had a perfect alibi: he'd been at work. On the way back he
- turns on his show, only to discover that the record is skipping.
- 1.15a. Variant: The music stops and the man dies. Answer: The same,
- except it's a tape breaking instead of a record skipping. (from Michael
- Killianey) (See also #1.16, #1.19e, and #1.34a.)
-
- 1.16. The woman is a tightrope walker in a circus. Her act consists of
- walking the rope blindfolded, accompanied by music, without a net. The
- musician (organist, or calliopist, or pianist, or whatever) is supposed to
- stop playing when she reaches the end of the rope, telling her that it's
- safe to step off onto the platform. For unknown reasons (but with
- murderous intent), he stops the music early, and she steps off the rope to
- her death.
- 1.16a. Variant answer: The woman is a character in an opera, who "dies"
- at the end of her song.
- 1.16b. Variant answer: The "woman" is the dancing figure atop a music
- box, who "dies" when the box runs down. (Both of the above variants would
- probably require placing this puzzle in section 2 of the list.)
- 1.16c. Variant: Charlie died when the music stopped. Answer: Charlie was
- an insect sitting on a chair; the music playing was for the game Musical
- Chairs. (from Bob Philhower)
- (See also #1.15a, #1.19e, and #1.34a.)
-
- 1.17. The man is a blind midget, the shortest one in the circus. Another
- midget, jealous because he's not as short, has been sawing small pieces
- off of the first one's cane every night, so that every day he thinks he's
- taller. Since his only income is from being a circus midget, he decides
- to kill himself when he gets too tall.
- 1.17a. Slightly variant answer: Instead of sawing pieces off of the
- midget's cane, someone has sawed the legs off of his bed. He wakes up,
- stands up, and thinks he's grown during the night.
- 1.17b. Variant: A pile of sawdust, no net, a man dies. Answer: A midget
- is jealous of the clown who walks on stilts. He saws partway through the
- stilts; the clown walks along and falls and dies when they break. (from
- Peter R. Olpe)
- 1.17c. Rough sketch of variant: There were a mirror and a bottle on the
- table, and sawdust on the floor. He came in and dropped dead. Answer: He
- was a midget, but he wasn't aware of it, because the table used to be too
- high for him to see his reflection in the mirror, until someone shortened
- its legs. He was horrified by the discovery, and the shock killed him.
- (vaguely remembered by Ivan A Derzhanski, who adds that this would be best
- used as raw material for some elaboration. I agree; it's pretty
- implausible as is)
-
- 1.18. The man is a lion-tamer, posing for a photo with his lions. The
- lions react badly to the flash of the camera, and the man can't see
- properly, so he gets mauled.
- 1.18a. Variant: He couldn't find a chair, so he died. Answer: He was a
- lion-tamer. This one is kind of silly, but I like it, and it sounds
- possible to me (though I'm told a whip is more important than a chair to a
- lion-tamer). (from "Reaper Man," with Karl Heuer wording)
-
- 1.19. A blind man enjoys walking near a cliff, and uses the sound of a
- buoy to gauge his distance from the edge. One day the buoy's anchor rope
- breaks, allowing the buoy to drift away from the shore, and the man walks
- over the edge of the cliff.
- 1.19a. Variant: A bell rings. A man dies. A bell rings. Answer: A
- blind swimmer sets an alarm clock to tell him when and what direction to
- go to shore. The first bell is a buoy, which he mistakenly swims to,
- getting tired and drowning. Then the alarm clock goes off. In other
- variations, the first bell is a ship's bell, and/or the second bell is a
- hand-bell rung by a friend on shore at a pre-arranged time.
- 1.19b. Variant answer to 1.19a: The man falls off a belltower, pulling
- the bell-cord (perhaps he was climbing a steeple while hanging onto the
- rope), and dies. The second bell is one rung at his funeral. Could also
- be a variant on 1.19 (as suggested by Mike Neergaard): the bell-cord
- breaks when he falls (and there's no second bell involved).
- 1.19c. Variant answer to 1.19a: The man is a boxer. The first bell
- signals the start of a round; the second is either the end of the round or
- a funeral bell after he dies during the match. Could also be a variant on
- 1.19 (as suggested by Mike Neergaard): a boxing match in which the top
- rope breaks, tumbling a boxer to the floor (and he dies of a concussion).
- 1.19d. Variant: The wind stopped blowing and the man died. Answer: The
- sole survivor of a shipwreck reached a desert isle. Unfortunately, he was
- blind. Luckily, there was a freshwater spring on the island, and he
- rigged the ship's bell (which had drifted to the island also) at the
- spring's location. The bell rang in the wind, directing him to water.
- When he was becalmed for a week, he could not find water again, and so he
- died of thirst. (from Peter R. Olpe)
- 1.19e. Variant: The music stopped and the man died. Answer: Same as
- 1.19a, but the blind swimmer kept a portable transistor radio on the beach
- instead of a bell. When the batteries gave out, he got lost and drowned.
- (from Joe Kincaid) (See also #1.15a, #1.16, and #1.34a.)
-
- 1.20. The woman is the assistant to a (circus or sideshow) knife thrower.
- The new shoes have higher heels than she normally wears, so that the
- thrower misjudges his aim and one of his knives kills her during the show.
-
- 1.21. Several men were shipwrecked together. They agreed to survive by
- eating each other a piece at a time. Each of them in turn gave up an arm,
- but before they got to the last man, they were rescued. They all demanded
- that the last man live up to his end of the deal. Instead, he killed a
- bum and sent the bum's arm to the others in a box to "prove" that he had
- fulfilled the bargain. Later, one of them sees him on the subway, holding
- onto an overhead ring with the arm he supposedly cut off; the other
- realizes that the last man cheated, and kills him.
- 1.21a. Variant wording: A man sends a package to someone in Europe and
- gets a note back saying "Thank you. I received it." Answer: This is just
- a simpler version; the shipwreck situation is the same, and the man
- actually did send his own arm.
- 1.21b. Variant wording: Two men throw a box off of a cliff. Answer:
- Exactly the same situation as in 1.21a (one slight variation has a hand in
- the box instead of a whole arm), with the two men being two of the fellow
- passengers who had already lost their arms.
- 1.21c. Variant wording: A man in a Sherlock Holmes-style cape walks
- into a room, places a box on the table and leaves. Answer: In this one
- he's wearing the cape either to disguise the fact that he hasn't really
- cut off his arm/hand as required, or else simply in order to hide his
- now-missing limb. (from Joe Kincaid)
-
- 1.22. Both women are white; the one whose house this takes place in is
- single. A black friend of the other woman, the one who goes into the
- bathroom, was recently killed, reportedly by the KKK. The woman who goes
- into the bathroom discovers a bloodstained KKK robe in the other's laundry
- hamper, picks up a nail file from the medicine cabinet (or some other
- impromptu weapon), and goes out and kills the other.
- 1.22a. Variant: A man goes to hang his coat and realises he will die that
- day. Answer: The man (who is black) has car trouble and is in need of a
- telephone. He asks at the nearest house and on being invited in goes to
- hang his coat, whereupon he notices the white robes of the Ku Klux Klan in
- the closet. (from Bernd Wechner)
-
- 1.23. He is in a hotel, and is unable to sleep because the man in the
- adjacent room is snoring. He calls the room next door (from his own
- room number he can easily figure out his neighbor's, and from the room
- number, the telephone number). The snorer wakes up, answers the phone.
- The first man hangs up without saying anything and goes to sleep before
- the snorer gets back to sleep and starts snoring again.
- 1.23a. Slightly variant answer: It's a next-door neighbor in an apartment
- building who's snoring, rather than in a hotel. The caller thus knows his
- neighbor and the phone number.
-
- 1.24. It's the man's fiftieth birthday, and in celebration of this he
- plans to kill his wife, then take the money he's embezzled and move on to
- a new life in another state. His wife takes him out to dinner; afterward,
- on their front step, he kills her. He opens the door, dragging her body
- in with him, and all the lights suddenly turn on and a group of his
- friends shout "Surprise!" He kills himself. (Note that the whole first
- part, including the motive, isn't really necessary; it was just part of
- the original story.)
-
- 1.25. Abel is a prince of the island nation that he landed on. A cruel
- and warlike prince, he waged many land and naval battles along with his
- father the king. In one naval encounter, their ship sank, the king died,
- and the prince swam to a deserted island where he spent several months
- building a raft or small boat. In the meantime, a regent was appointed to
- the island nation, and he brought peace and prosperity. When Prince Abel
- returned to his kingdom, Cain (a native fisherman) realized that the peace
- of the land would only be maintained if Abel did not reascend to his
- throne, and killed the prince (with a piece of driftwood or some other
- impromptu weapon).
-
- 1.26. The drinks contain poisoned ice cubes; one man drinks slowly,
- giving them time to melt, while the other drinks quickly and thus doesn't
- get much of the poison. The fact that they drink at different speeds
- could be added to the statement, possibly along with red herrings such as
- saying that one of the men is big and burly and the other short and thin.
-
- 1.27. Joe is a kid who goes trick-or-treating for Halloween.
-
- 1.28. He's a smuggler. On the first cruise, someone brings the
- contraband to his cabin, and he hides it in an air conditioning duct.
- Returning to the U.S., he leaves without the contraband, and so passes
- through customs with no trouble. On the second trip, he has the same
- cabin on the same ship. Because it doesn't stop anywhere, he doesn't have
- to go through customs when he returns, so he gets the contraband off
- safely.
-
- 1.29. Hans and Fritz do everything right up until they're filling out a
- personal-information form and have to write down their birthdays. Fritz'
- birthday is, say, July 7, so he writes down 7/7/15. Hans, however, was
- born on, say, June 20, so he writes down 20/6/18 instead of what an
- American would write, 6/20/18. Note that this is only a problem because
- they *claim* to be returning Americans; as has been pointed out to me,
- there are lots of other nations which use the same date ordering.
-
- 1.30. Another WWII story. Greg is a German spy. His "friend" Tim is
- suspicious, so he plays a word-association game with him. When Tim says
- "The land of the free," Greg responds with "The home of the brave." Then
- Tim says "The terror of flight," and Greg says "The gloom of the grave."
- Any U.S. citizen knows the first verse of the national anthem, but only a
- spy would have memorized the third verse. (Why Tim knew the third verse
- is left as an exercise to the reader.)
-
- 1.31. The dead man was the driver in a hit-and-run acccident which
- paralyzed its victim. The victim did manage to get the license plate
- number of the car; now in a wheelchair, he eventually tracked down the
- driver and shot and killed him.
-
- 1.32. His home is a houseboat and he has run out of water while on an
- extended cruise.
- 1.32a. Variant wording: A man dies of thirst in his own home. This
- version goes more quickly because it gives more information; but it may be
- less likely to annoy people who think the original statement is too vague.
-
- 1.33. I'm told this is a true story. Windows in Paris at that time were
- apparently imperfectly flat; they could act as lenses. One particularly
- hot day, the sun shining in through such a window caused a woman's
- lingerie (which she was wearing at the time, awaiting her husband's
- return) to catch fire, and eventually the entire house caught and burned.
-
- 1.34. He's leaving a hospital after visiting his wife, who's on heavy
- life-support. When the power goes out, he knows she can't live without
- the life-support systems (he assumes that if the emergency backup
- generator were working, the elevator wouldn't lose power; this aspect
- isn't entirely satisfactory, so in a variant, the scene is at home rather
- than in a hospital).
- 1.34a. Variant: The music stops and a woman dies. Answer: The woman is
- confined in an iron lung, and the music is playing on her radio or stereo.
- The power goes out. (from Randy Whitaker) (See also #1.15a, #1.16, and
- #1.19e.)
-
- 1.35. A large man comes home to the penthouse apartment he shares with
- his beautiful young wife, taking the elevator up from the ground floor.
- He sees signs of lovemaking in the bedroom, and assumes that his wife is
- having an affair; her beau has presumably escaped down the stairs. The
- husband looks out the French windows and sees a good-looking man just
- leaving the main entrance of the building. The husband pushes the
- refrigerator out through the window onto the young man below. The husband
- dies of a heart attack from overexertion; the young man below dies from
- having a refrigerator fall on him; and the wife's boyfriend, who was
- hiding inside the refrigerator, also dies from the fall.
-
- 1.36. Let's say "she" is named Suzy, and "they" are named Harry and Jane.
- Harry is an elderly archaeologist who has found a very old skeleton, which
- he's dubbed "Jane" (a la "Lucy"). Suzy is a buyer for a museum; she's
- supposed to make some sort of purchase from Harry, so she invites him to
- have a business dinner with her (at a restaurant). When she calls to
- invite him, he keeps talking about "Jane," so Suzy assumes that Jane is
- his wife and says to bring her along. Harry, offended, calls Suzy's boss
- and complains; since Suzy should've known who Jane was, she gets fired.
-
- 1.37. The man is delivering a pardon, and the flicker of the lights
- indicates that the person to be pardoned has just been electrocuted.
-
- 1.38. The murderer sets the car on a slope above the hot dog stand where
- the victim works. He then wedges an ice block in the car to keep the
- brake pedal down, and puts the car in neutral, after which he flies to
- another city to avoid suspicion. It's a warm day; when the ice melts, the
- car rolls down the hill and strikes the hot dog man at his roadside stand,
- killing him.
-
- 1.39. There's a car wash on that corner. On rainy days, the rain reduces
- traction. On sunny days, water from the car wash has the same effect. If
- rain is threatening, though, the car wash gets little business and thus
- doesn't make the road wet, so I can take the corner faster.
-
- 1.40. The object she throws is a boomerang. It flies out, loops around,
- and comes back and hits her in the head, killing her. Boomerangs do not
- often return so close to the point from which they were thrown, but I
- believe it's possible for this to happen.
- 1.40a. Silly variant answer: She's in a submarine or spacecraft and
- throws a heavy object at the window, which breaks.
-
- 1.41. He is a passenger in an airplane and sees the bird get sucked into
- an engine at 20,000 feet.
-
- 1.42. They're the remains of a melted snowman.
-
- 1.43. One of the brothers (A) confesses to the murder. At his trial, his
- brother (B) is called as the only defense witness; B immediately
- confesses, in graphic detail, to having committed the crime. The defense
- lawyer refuses to have the trial stopped, and A is acquitted under the
- "reasonable doubt" clause. Immediately afterward, B goes on trial for the
- murder; A is called as the only defense witness and HE confesses. B is
- declared innocent; and though everyone knows that ONE of them did it, how
- can they tell who? Further, neither can be convicted of perjury until
- it's decided which of them did it... I don't know if that would actually
- work under our legal system, but someone else who heard the story said
- that his father was on the jury for a VERY similar case in New York some
- years ago. Mark Brader points out that the brothers might be convicted of
- conspiracy to commit perjury or to obstruct justice, or something of that
- kind.
-
- 1.44. He is a mail courier who delivers packages to the different foreign
- embassies in the United States. The land of an embassy belongs to the
- country of the embassy, not to the United States.
-
- 1.45. A man was shot during a robbery in his store one night. He
- staggered into the back room, where the telephone was, and called home,
- dialing by feel since he hadn't turned on the light. Once the call went
- through he gasped, "I'm at the store. I've been shot. Help!" or words to
- that effect. He set the phone down to await help, but none came; he'd
- treated the telephone pushbuttons like cash register numbers, when the
- arrangements of the numbers are upside down reflections of each other.
- The stranger he'd dialed had no way to know where "the store" was.
-
- 1.46. The dead man was playing Santa Claus, for whatever reason; he
- slipped while coming down the chimney and broke his neck.
- 1.46a. Variant answer: The dead man WAS Santa Claus. This moves the
- puzzle to section 2.
-
- 1.47. The man was struck by an object thrown from the roof of the Empire
- State Building. Originally I had the object being a penny, but several
- people suggested that a penny probably wouldn't be enough to penetrate
- someone's skull. Something aerodynamic and heavier, like a dart, was
- suggested, but I don't know how much mass would be required.
- 1.47a. Variant: A man is found dead outside a large marble building with
- three holes in him. Answer: The man was a paleontologist working with the
- Archaeological Research Institute. He was reviving a triceratops frozen
- in the ice age when it came to life and killed him. This couldn't
- possibly happen because triceratops didn't exist during the ice age.
- (from Peter R. Olpe)
-
- 1.48. The man died from eating a poisoned popsicle.
-
- 1.49. The man was a sword swallower in a carnival side-show. While he
- was practicing, someone tickled his throat with the feather, causing him
- to gag.
-
- 1.50. A mosquito bit me, and I swatted it when it later landed on my
- ceiling (so the blood is my own as well as the mosquito's).
-
- 1.51. The man is a lighthouse keeper. He turns off the light in the
- lighthouse and during the night a ship crashes on the rocks. Seeing this
- the next morning, the man realizes what he's done and commits suicide.
- 1.51a. Variant, similar to #1.15: The light goes out and a man dies.
- Answer: The lighthouse keeper uses his job as an alibi while he's
- elsewhere committing a crime, but the light goes out and a ship crashes,
- thereby disproving the alibi. The lighthouse keeper kills himself when he
- realizes his alibi is no good. (From Eric Wang)
- 1.51b. Variant answer to 1.51a: Someone else's alibi is disproven. (A
- man commits a heinous crime, claiming as his alibi that he was onboard a
- certain ship. When he learns that it was wrecked without reaching port
- safely, he realizes that his alibi is disproven and commits suicide to
- avoid being sent to prison.) (From Eric Wang)
-
- 1.52. They were skydiving. He broke his arm as he jumped from the plane
- by hitting it on the plane door; he couldn't reach his ripcord with his
- other arm. She pulled the ripcord for him.
- 1.52a. Sketch of variant answer: The ring was attached to the pin of a
- grenade that he was holding. Develop a situation from there.
-
- 1.53. The man is a travel agent. He had sold someone two tickets for an
- ocean voyage, one round-trip and one one-way. The last name of the man
- who bought the tickets is the same as the last name of the woman who
- "fell" overboard and drowned on the same voyage, which is the subject of
- the article he's reading.
-
- 1.54. The man is a beekeeper, and the bees attack en masse because they
- don't recognize his fragrance. Randy adds that this is based on something
- that actually happened to his grandfather, a beekeeper who was severely
- attacked by his bees when he used a new aftershave for the first time in 10
- or 20 years.
-
- 1.55. He is a guard / attendant in a leper colony. The letter (to him)
- tells him that he has contracted the disease. The key is the cigarette
- burning down between his fingers -- leprosy is fairly unique in killing off
- sensory nerves without destroying motor ability. (Randy was told this by
- Gary Haas and Chris Englehard)
-
- 1.56. The man was a famous artist. A woman who collected autographs saw
- him dining; after he left the restaurant, she purchased the check that he
- used to pay for the meal from the restaurant manager. The check was
- therefore never cashed, so the artist never paid for the meal.
-
- 1.57. The movie is at a drive-in theatre.
-
-
- Section 2: Double meanings, fictional settings, and miscellaneous others.
-
- 2.1. The man is a heroin addict, and has contracted AIDS by using an
- infected needle. In despair, he shoots himself up with an overdose,
- thereby committing suicide.
-
- 2.2. The man walks into a casino and goes to the craps table. He bets
- all the money he owns, and shoots craps. Since he is now broke, he
- becomes despondent and commits suicide.
-
- 2.3. Kids getting their pictures taken with Santa. I see #2.1, #2.2, and
- #2.3 as different enough from each other to merit separate numbers,
- although they all rely on the same basic gimmick of alternate meanings of
- the word "shoot."
-
- 2.4. It's the cabin of an airplane that crashed there because of the
- snowstorm.
- 2.4a. Variant wording: A cabin, on the side of a mountain, locked from
- the inside, is opened, and 30 people are found dead inside. They had
- plenty of food and water. (from Ron Carter)
-
- 2.5. He's a priest; he is marrying them to other people, not to himself.
-
- 2.6. The "island" is a traffic island.
-
- 2.7. A baseball game is going on. The base-runner sees the catcher
- waiting at home plate with the ball, and so decides to stay at third base
- to avoid being tagged out.
- 2.7a. Variant: Two men are in a field. One is wearing a mask. The other
- man is running towards him to avoid him. Answer: the same, but the
- catcher isn't right at home plate; the runner is trying to get home before
- the catcher can. (from Hal Lowery, by way of Chris Riley) This phrasing
- would allow the puzzle to migrate to section 1, but I don't like it as
- much.
-
- 2.8. The man is an astronaut out on a space walk.
-
- 2.9. The man was an amateur mechanic, the book is a Volkswagen service
- manual, the beetle is a car, and the pile of bricks is what the car fell
- off of.
-
- 2.10. The Eagle landed in the Sea of Tranquility and will likely remain
- there for the foreseeable future.
-
- 2.11. It's a wolf pack; they've killed and eaten (most of) the man.
-
- 2.12. The dead man is Superman; the rock is Green Kryptonite. Invent a
- reasonable scenario from there.
-
- 2.13. This is a post-holocaust scenario of some kind; for whatever
- reason, the man believes himself to be the last human on earth. He
- doesn't want to live by himself, so he jumps, just before the telephone
- rings... (of course, it could be a computer calling, but he has no way of
- knowing).
-
- 2.14. The one who looks around sees his own reflection in the window
- (it's dark outside), but not his companion's. Thus, he realizes the other
- is a vampire, and that he's going to be killed by him.
-
- 2.15. The "bicycles" are Bicycle playing cards; the man was cheating at
- cards, and when the extra card was found, he was killed by the other
- players.
- 2.15a. Variant: There are 53 bees instead of 53 bicycles. Answer: The
- same (Bee is another brand of playing cards).
- 2.15b. Variant: There are 51 instead of 53. Answer: Someone saw the guy
- conceal a card, and proved the deck was defective by turning it up and
- pointing out the missing ace. Or, the game was bridge, and the others
- noticed the cheating when the deal didn't come out even. The man had
- palmed an ace during the shuffle and meant to put it in his own hand
- during the deal, but muffed it. (both answers from Mark Brader)
-
- 2.16. A chess game; knight takes pawn.
- 2.16a. Variant: It's the year 860 A.D., at Camelot. Two priests are
- sitting in the castle's chapel. The queen attacks the king. The two
- priests rise, shake hands, and leave the room. Answer: The two priests
- are playing chess; one of them just mated by moving his queen. (from
- Ellen M. Sentovich)
- 2.16b. Variant: A black leader dies in Africa. Answer: The black leader
- is a chess king, and the game was played in Africa. (from Erick
- Brethenoux)
-
- 2.17. It's a model train set.
- 2.17a. Variant: The Orient Express is derailed and a kitten plays nearby.
- Answer: The Orient Express is a model train which has been left running
- unattended. The kitten has playfully derailed it. (from Bernd Wechner)
-
- 2.18. It's a game of Monopoly.
-
- 2.19. The sun is shining; there's no rain.
-
- 2.20. It's daytime; the sun is out.
-
- 2.21. Alice is a goldfish; Ted is a cat.
- 2.21a. A very common variant uses the names Romeo and Juliet instead, to
- further mislead audiences. For example: Romeo is looking down on Juliet's
- dead body, which is on the floor surrounded by water and broken glass.
- (from Adam Carlson)
- 2.21b. Minor variant: Tom and Jean lay dead in a puddle of water with
- broken pieces of glass and a baseball nearby. Answer: Tom and Jean are both
- fish; it was a baseball, rather than a cat, that broke their tank. (from
- Mike Reymond)
-
- 2.22. Friday is a horse.
- 2.22a. Variant with the same basic gimmick: A woman comes home, sees
- Spaghetti on the wall and kills her husband. Answer: Spaghetti was the
- name of her pet dog. Her husband had it stuffed and mounted after it made
- a mess on his rug. (Simon Travaglia original)
-
- 2.23. Bruce is a horse.
-
- 2.24. Should be done orally; the envelope is an evelope of dye, and she's
- dying some cloth, but it sounds like "opens an envelope and dies" if said
- out loud.
-
- 2.25. The native chief asked him, "What is the third baseman's name in
- the Abbot and Costello routine 'Who's on First'?" The man, who had no
- idea, said "I don't know," the correct answer. However, he was a major
- smartass, so if he had known the answer he would have pointed out that
- What was the SECOND baseman's name. The chief, being quite humorless,
- would have executed him on the spot. This is fairly silly, but I like it
- too much to remove it from the list.
-
- 2.26. The men have gone spelunking and have taken an Igloo cooler with
- them so they can have a picnic down in the caves. They cleverly used dry
- ice to keep their beer cold, not realizing that as the dry ice sublimed
- (went from solid state to vapor state) it would push the lighter oxygen
- out of the cave and they would suffocate.
-
- ==> logic/smullyan/black.hat.p <==
- Three logicians, A, B, and C, are wearing hats, which they know are either
- black or white but not all white. A can see the hats of B and C; B can see
- the hats of A and C; C is blind. Each is asked in turn if they know the color
- of their own hat. The answers are:
- A: "No."
- B: "No."
- C: "Yes."
- What color is C's hat and how does she know?
-
- ==> logic/smullyan/black.hat.s <==
- A must see at least one black hat, or she would know that her hat is black
- since they are not all white. B also must see at least one black hat, and
- further, that hat had to be on C, otherwise she would know that her
- hat was black (since she knows A saw at least one black hat). So C knows
- that her hat is black, without even seeing the others' hats.
-
- ==> logic/smullyan/fork.three.men.p <==
- Three men stand at a fork in the road. One fork leads to Someplaceorother;
- the other fork leads to Nowheresville. One of these people always answers
- the truth to any yes/no question which is asked of him. The other always
- lies when asked any yes/no question. The third person randomly lies and
- tells the truth. Each man is known to the others, but not to you.
- What is the least number of yes/no questions you can ask of these men and
- pick the road to Someplaceorother?
-
- ==> logic/smullyan/fork.three.men.s <==
- It is clear that you must ask at least two questions, since you might be
- asking the first one of the randomizer and there is nothing you can tell
- from his answers.
-
- Start by asking A "Is B more likely to tell the truth than C?"
-
- If he answers "yes", then:
- If A is truthteller, B is randomizer, C is liar.
- If A is liar, B is randomizer, C is truthteller.
- If A is randomizer, C is truthteller or liar.
-
- If he answers "no", then:
- If A is truthteller, B is liar, C is randomizer.
- If A is liar, B is truthteller, C is randomizer.
- If A is randomizer, B is truthteller or liar.
-
- In either case, we now know somebody (C or B, respectively) who is either
- a truthteller or liar. Now, use the technique for finding information from
- a truthteller/liar, viz.:
-
- You ask him the following question: "If I were to ask a person of the opposite
- type to yourself if the left fork leads to Someplacerother, would he say yes?"
-
- If the person asked is a truthteller, he will tell you what a liar would
- say, which would be the wrong information. If the person asked is a liar,
- he will either tell you what a liar would say, or he will lie about what a
- truthteller would say. In either case, he will report the wrong information.
- If the answer is yes, take the right fork, if no take the left fork.
-
- ==> logic/smullyan/fork.two.men.p <==
- Two men stand at a fork in the road. One fork leads to Someplaceorother; the
- other fork leads to Nowheresville. One of these people always answers the
- truth to any yes/no question which is asked of him. The other always lies
- when asked any yes/no question. By asking one yes/no question, can you
- determine the road to Someplaceorother?
-
- ==> logic/smullyan/fork.two.men.s <==
- The question to ask is: "Will the other person say the right fork leads to
- Someplaceorother?" If the person asked says yes, then take the left fork,
- else take the right fork.
-
- If the person asked is the truthteller, then he correctly reports that the
- liar will misinform you about the right fork. If he is the liar, then he
- lies about what the truthteller will say. Either way, you should go the
- opposite direction from the way that the person asked says the other person
- will answer.
-
- The fact that there are two is a red herring - you only need one of
- either type. You ask him the following question: "If I were to ask a
- person of the opposite type to yourself if the left fork leads to
- Someplacerother, would he say yes?"
-
- If the person asked is a truthteller, he will tell you what a liar would
- say, which would be the wrong information. If the person asked is a liar,
- he will either tell you what a liar would say, or he will lie about what a
- truthteller would say. In either case, he will report the wrong information.
- If the answer is yes, take the right fork, if no take the left fork.
-
- This solution also removes the problem that the men may not know the
- other's identity.
-
- It is possible, of course, that the liars are malicious, and they will tell
- the truth if they figure out that you are trying to trick them.
-
-
- ==> logic/smullyan/integers.p <==
- Two logicians place cards on their foreheads so that what is written on the
- card is visible only to the other logician. Consecutive positive integers
- have been written on the cards. The following conversation ensues:
- A: "I don't know my number."
- B: "I don't know my number."
- A: "I don't know my number."
- B: "I don't know my number."
- ... n statements of ignorance later ...
- A or B: "I know my number."
- What is on the card and how does the logician know it?
-
- ==> logic/smullyan/integers.s <==
- If A saw 1, she would know that she had 2, and would say so. Therefore,
- A did not see 1. A says "I don't know my number."
- If B saw 2, she would know that she had 3, since she knows that A did not see
- 1, so B did not see 1 or 2. B says "I don't know my number."
- If A saw 3, she would know that she had 4, since she knows that B did not
- see 1 or 2, so A did not see 1, 2 or 3. A says "I don't know my number."
- If B saw 4, she would know that she had 5, since she knows that A did not
- see 1, 2 or 3, so B did not see 1, 2, 3 or 4. B says "I don't know my number."
- ... n statements of ignorance later ...
- If X saw n, she would know that she had n + 1, since she knows that ~X did not
- see 1 ... n - 1, so X did see n. X says "I know my number."
-
- And the number in n + 1.
-
- ==> logic/smullyan/liars.et.al.p <==
- Of a group of n men, some always lie, some never lie, and the rest sometimes
- lie. They each know which is which. You must determine the identity of each
- man by asking the least number of yes-or-no questions.
-
- ==> logic/smullyan/liars.et.al.s <==
- The real problem is to isolate the sometimes liars.
-
- Consider the case of three men:
- Ask man 1: "Does man 2 lie more than 3?"
- If the answer is yes, then man 2 cannot be the sometimes liar.
- Proof by analyzing the cases:
- Case 1: Man 2 is not the sometimes liar.
- Case 2: Man 2 is the sometimes liar, man 1 is the truth teller, and man 3 is
- the liar. Then man 1 would not say that man 2 lies more than man 3.
- Case 3: Man 2 is the sometimes liar, man 3 is the truth teller, and man 1 is
- the liar. Then man 1 would not say that man 2 lies more than man 3.
- QED.
- Similarly, if the answer is no, then man 3 cannot be the sometimes liar.
- Now ask the symmetric question of whichever man has been eliminated as the
- sometimes liar. The answer will now allow you to determine the identity
- of the sometimes liar. To determine the identity of the two remaining men, ask
- some question like "Does 1=1?" which is always true.
-
- This is not the only way to solve this problem. You could have asked the
- question which is always true (or false) second, which would now establish
- the identity of either the liar or the truth teller. Then ask the third
- question of this man to find out which of the other two is the sometimes
- liar.
-
- This problem requires three questions, whether or not they are yes-or-no
- questions. In order to identify all three men, you must identify the
- sometimes liar. You cannot identify the sometimes liar in one question
- since you may be asking it of the sometimes liar, and any answer from him
- conveys no information at all. Therefore at least two questions are
- necessary to identify the sometimes liar. Once the sometimes liar is
- identified, you still need one more question at least to identify the
- remaining men. Therefore, three questions are required.
-
- Suppose we have two truth-tellers, two liars, and two randomizers.
- The answer is 8. A proof follows.
-
- For brevity, "T" means truth-teller, "L" liar, "R" randomizer, "P" predictable
- (either T or L). Define a _pattern_ to be one of the C(6,2)=15 permutations
- of RRPPPP (each of which has C(4,2)=6 interpretations of the Ps as 2 Ts and 2
- Ls). For any question Q, let !Q denote the question "If I were to ask you Q,
- would you answer Yes?". Note that question !Q directed toward any P will
- yield a truthful answer to question Q; in other words, a "Yes" answer to !Q
- means that either Q is true or the respondent is an R, whereas "No" means that
- either Q is false or the respondent is an R.
-
- Ask #1, !"Are both Rs in the set {#2, #3, #4}?". "No" implies that at most
- one of {#2, #3, #4} is an R. "Yes" implies that at most one of {#2, #5, #6}
- is an R. Without loss of generality, assume the former.
-
- Ask #2, !"Is #3 an R?". "No" implies that #3 is a P. "Yes" implies that #4
- is a P.
-
- Having identified someone as a P, there are at most C(5,2)=10 possible
- patterns, and hence at most 10*6=60 possible results. We can determine which
- one reflects reality with at most 6 more questions with a binary search. (At
- each step, bisect the set of possible answers, and ask the question !"Is the
- correct pattern in the first subset?".)
-
- Now, let's show that it can't be done in 7.
-
- After asking your first two questions, renumber if necessary so that the first
- question was directed to #1 and the second to #2. (If you asked the same
- person twice, you're even worse off than in the analysis below.) You have no
- way to rule out the possibility that both are Rs, so pattern RRPPPP yields 6
- possibilities. Of the four patterns RPRPPP RPPRPP RPPPRP RPPPPR, your first
- question gave no information and the second had one bit; so at best you can
- eliminate half of these 4*6 possibilities, leaving 12. Similarly for the four
- patterns PRRPPP PRPRPP PRPPRP PRPPPR there remain at least 12 possibilities.
- Of the remaining 6 patterns PPRRPP PPRPRP PPRPPR PPPRRP PPPRPR PPPPRR, your
- two bits of information can eliminate 3/4 of the 6*6, leaving 9. Thus, after
- two questions there are at least 6+12+12+9=39 arrangements that could have
- given the answers you heard; your five remaining questions have only 32
- possible replies, so you can't distinguish them.
-
- ==> logic/smullyan/painted.heads.p <==
- While three logicians were sleeping under a tree, a malicious child painted
- their heads red. Upon waking, each logician spies the child's handiwork as
- it applied to the heads of the other two. Naturally they start laughing.
- Suddenly one falls silent. Why?
-
- ==> logic/smullyan/painted.heads.s <==
- The one who fell silent, presumably the quickest of the three, reasoned
- that his head must be painted also. The argument goes as follows.
- Let's call the quick one Q, and the other two D and S. Let's assume
- Q's head is untouched. Then D is laughing because S's head is painted,
- and vice versa. But eventually, D and S will realize that their head
- must be painted, because the other is laughing. So they will quit
- laughing as soon as they realize this. So, Q waits what he thinks is
- a reasonable amount of time for them to figure this out, and when they
- don't stop laughing, his worst fears are confirmed. He concludes that
- his assumption is invalid and he must be crowned in crimson too.
-
-
- ==> logic/smullyan/priest.p <==
- A priest takes confession of all the inhabitants in a small town. He
- discovers that in N married pairs in the town, one of the pair has
- committed adultery. Assume that the spouse of each adulterer does not
- know about the infidelity of his or her spouse, but that, since it is
- a small town, everyone knows about everyone else's infidelity. In
- other words, each spouse of an adulterer thinks there are N - 1
- adulterers, but everyone else thinks there are N adulterers. The
- priest, who is an Old Testament type, decides that he should do
- something about the situation. He cannot break the confessional, but
- being an amateur logician of sorts, he hits upon a plan to do God's
- work. He announces in Mass one Sunday that the spouse of each
- adulterer has the moral obligation to punish his or her adulterous
- spouse by publicly denouncing them in church, and that he will make
- time during his next Sunday service for this, and continue to do so
- until all adulterers have been denounced. Is the priest correct? Will
- this result in every adulterer being denounced?
-
- ==> logic/smullyan/priest.s <==
- Yes. Let's start with the simple case that N = 1. The offended spouse
- reasons as follows: the priest knows there is at least one adulterer,
- but I don't know who this person is, and I would if it were anyone
- other than me, so it must be me. What happens if N = 2? On the first
- Sunday, the two offended spouses each calmly wait for the other to get
- up and condemn their spouses. When the other doesn't stand, they
- think: They do not think that they are a victim. But if they do not
- think they are victims, then they must think there are no adulterers,
- contrary to what the priest said. But everyone knows the priest speaks
- with the authority of God, so it is unthinkable that he is mistaken.
- The only remaining possibility is that they think there WAS another
- adulterer, and the only possibility is: MY SPOUSE! So, they know that
- they too must be victims. So on the next Sunday, they will get up.
- What if N = 3? On the first Sunday, each victim waits for the other
- two to get up. When they do not, they assume that they did not get up
- because they did not know about the other person (in other words, they
- hypothesize that each of the two other victims thought there was only
- one adulterer). However, each victim reasons, the two will now realize
- that they must be two victims, for the reasons given under the N = 2
- case above. So they will get up next Sunday. This excuse lasts until
- the next Sunday, when still no one gets up, and now each victim
- realizes that either the priest was mistaken (unthinkable!) or there
- are really three victims, and I am ONE! So, on the third Sunday, all
- three get up. This reasoning can be repeated inductively to show that
- no one will do anything (except use up N - 1 excuses as to why no one
- got up) until the Nth Sunday, when all N victims will arise in unison.
-
- By the way, the rest of the town, which thinks there are N adulterers,
- is about to conclude that their perfectly innocent spouses have been
- unfaithful too. This includes the adulterous spouses, who are about to
- conclude that the door swings both ways. So the priest is playing a
- dangerous game. A movie plot in there somewhere?
-
- ==> logic/smullyan/stamps.p <==
- The moderator takes a set of 8 stamps, 4 red and 4 green, known to the
- logicians, and loosely affixes two to the forehead of each logician so that
- each logician can see all the other stamps except those 2 in the moderator's
- pocket and the two on her own head. He asks them in turn
- if they know the colors of their own stamps:
- A: "No"
- B: "No"
- C: "No"
- A: "No
- B: "Yes"
- What are the colors of her stamps, and what is the situation?
-
- ==> logic/smullyan/stamps.s <==
- B says: "Suppose I have red-red. A would have said on her
- second turn: 'I see that B has red-red. If I also have red-red, then all
- four reds would be used, and C would have realized that she had green-green.
- But C didn't, so I don't have red-red. Suppose I have green-green. In that
- case, C would have realized that if she had red-red, I would have seen
- four reds and I would have answered that I had green-green on my first
- turn. On the other hand, if she also has green-green [we assume that
- A can see C; this line is only for completeness], then B would have seen
- four greens and she would have answered that she had two reds. So C would
- have realized that, if I have green-green and B has red-red, and if
- neither of us answered on our first turn, then she must have green-red.
- "'But she didn't. So I can't have green-green either, and if I can't have
- green-green or red-red, then I must have green-red.'
- So B continues: "But she (A) didn't say that she had green-red, so
- the supposition that I have red-red must be wrong. And as my logic applies
- to green-green as well, then I must have green-red."
- So B had green-red, and we don't know the distribution of the others
- certainly.
- (Actually, it is possible to take the last step first, and deduce
- that the person who answered YES must have a solution which would work
- if the greens and reds were switched -- red-green.)
-
- ==> logic/timezone.p <==
- Two people are talking long distance on the phone; one is in an East-
- Coast state, the other is in a West-Coast state. The first asks the other
- "What time is it?", hears the answer, and says, "That's funny. It's the
- same time here!"
-
- ==> logic/timezone.s <==
- One is in Eastern Oregon (in Mountain time), the other in
- Western Florida (in Central time), and it's daylight-savings
- changeover day at 1:30 AM.
-
- ==> logic/unexpected.p <==
- Swedish civil defense authorities announced that a civil defense drill would
- be held one day the following week, but the actual day would be a surprise.
- However, we can prove by induction that the drill cannot be held. Clearly,
- they cannot wait until Friday, since everyone will know it will be held that
- day. But if it cannot be held on Friday, then by induction it cannot be held
- on Thursday, Wednesday, or indeed on any day.
-
- What is wrong with this proof?
-
- ==> logic/unexpected.s <==
- This problem has generated a vast literature (see below). Several
- solutions of the paradox have been proposed, but as with most paradoxes
- there is no consensus on which solution is the "right" one.
-
- The earliest writers (O'Connor, Cohen, Alexander) see the announcement as
- simply a statement whose utterance refutes itself. If I tell you that I
- will have a surprise birthday party for you and then tell you all the
- details, including the exact time and place, then I destroy the surprise,
- refuting my statement that the birthday will be a surprise.
-
- Soon, however, it was noticed that the drill could occur (say on Wednesday),
- and still be a surprise. Thus the announcement is vindicated instead of
- being refuted. So a puzzle remains.
-
- One school of thought (Scriven, Shaw, Medlin, Fitch, Windt) interprets
- the announcement that the drill is unexpected as saying that the date
- of the drill cannot be deduced in advanced. This begs the question,
- deduced from which premises? Examination of the inductive argument
- shows that one of the premises used is the announcement itself, and in
- particular the fact that the drill is unexpected. Thus the word
- "unexpected" is defined circularly. Shaw and Medlin claim that this
- circularity is illegitimate and is the source of the paradox. Fitch
- uses Godelian techniques to produce a fully rigorous self-referential
- announcement, and shows that the resulting proposition is
- self-contradictory. However, none of these authors explain how it can
- be that this illegitimate or self-contradictory announcement
- nevertheless appears to be vindicated when the drill occurs. In other
- words, what they have shown is that under one interpretation of "surprise"
- the announcement is faulty, but their interpretation does not capture the
- intuition that the drill really is a surprise when it occurs and thus
- they are open to the charge that they have not captured the essence of
- the paradox.
-
- Another school of thought (Quine, Kaplan and Montague, Binkley,
- Harrison, Wright and Sudbury, McClelland, Chihara, Sorenson) interprets
- "surprise" in terms of "knowing" instead of "deducing." Quine claims
- that the victims of the drill cannot assert that on the eve of the last
- day they will "know" that the drill will occur on the next day. This
- blocks the inductive argument from the start, but Quine is not very
- explicit in showing what exactly is wrong with our strong intuition
- that everybody will "know" on the eve of the last day that the drill
- will occur on the following day. Later writers formalize the paradox
- using modal logic (a logic that attempts to represent propositions
- about knowing and believing) and suggest that various axioms about
- knowing are at fault, e.g., the axiom that if one knows something, then
- one knows that one knows it (the "KK axiom"). Sorenson, however,
- formulates three ingenious variations of the paradox that are
- independent of these doubtful axioms, and suggests instead that the
- problem is that the announcement involves a "blindspot": a statement
- that is true but which cannot be known by certain individuals even if
- they are presented with the statement. This idea was foreshadowed by
- O'Beirne and Binkley. Unfortunately, a full discussion of how this
- blocks the paradox is beyond the scope of this summary.
-
- Finally, there are two other approaches that deserve mention. Cargile
- interprets the paradox as a game between ideally rational agents and finds
- fault with the notion that ideally rational agents will arrive at the same
- conclusion independently of the situation they find themselves in. Olin
- interprets the paradox as an issue about justified belief: on the eve of
- the last day one cannot be justified in believing BOTH that the drill will
- occur on the next day AND that the drill will be a surprise even if both
- statements turn out to be true; hence the argument cannot proceed and the
- drill can be a surprise even on the last day.
-
- For those who wish to read some of the literature, good papers to start with
- are Bennett-Cargile and both papers of Sorenson. All of these provide
- overviews of previous work and point out some errors, and so it's helpful to
- read them before reading the original papers. For further reading on the
- "deducibility" side, Shaw, Medlin and Fitch are good representatives. Other
- papers that are definitely worth reading are Quine, Binkley, and Olin.
-
- D. O'Connor, "Pragmatic Paradoxes," Mind 57:358-9, 1948.
- L. Cohen, "Mr. O'Connor's 'Pragmatic Paradoxes,'" Mind 59:85-7, 1950.
- P. Alexander, "Pragmatic Paradoxes," Mind 59:536-8, 1950.
- M. Scriven, "Paradoxical Announcements," Mind 60:403-7, 1951.
- D. O'Connor, "Pragmatic Paradoxes and Fugitive Propositions," Mind 60:536-8,
- 1951
- P. Weiss, "The Prediction Paradox," Mind 61:265ff, 1952.
- W. Quine, "On A So-Called Paradox," Mind 62:65-7, 1953.
- R. Shaw, "The Paradox of the Unexpected Examination," Mind 67:382-4, 1958.
- A. Lyon, "The Prediction Paradox," Mind 68:510-7, 1959.
- D. Kaplan and R. Montague, "A Paradox Regained," Notre Dame J Formal Logic
- 1:79-90, 1960.
- G. Nerlich, "Unexpected Examinations and Unprovable Statements," Mind
- 70:503-13, 1961.
- M. Gardner, "A New Prediction Paradox," Brit J Phil Sci 13:51, 1962.
- K. Popper, "A Comment on the New Prediction Paradox," Brit J Phil Sci 13:51,
- 1962.
- B. Medlin, "The Unexpected Examination," Am Phil Q 1:66-72, 1964.
- F. Fitch, "A Goedelized Formulation of the Prediction Paradox," Am Phil Q
- 1:161-4, 1964.
- R. Sharpe, "The Unexpected Examination," Mind 74:255, 1965.
- J. Chapman & R. Butler, "On Quine's So-Called 'Paradox,'" Mind 74:424-5, 1965.
- J. Bennett and J. Cargile, Reviews, J Symb Logic 30:101-3, 1965.
- J. Schoenberg, "A Note on the Logical Fallacy in the Paradox of the
- Unexpected Examination," Mind 75:125-7, 1966.
- J. Wright, "The Surprise Exam: Prediction on the Last Day Uncertain," Mind
- 76:115-7, 1967.
- J. Cargile, "The Surprise Test Paradox," J Phil 64:550-63, 1967.
- R. Binkley, "The Surprise Examination in Modal Logic," J Phil 65:127-36,
- 1968.
- C. Harrison, "The Unanticipated Examination in View of Kripke's Semantics
- for Modal Logic," in Philosophical Logic, J. Davis et al (ed.), Dordrecht,
- 1969.
- P. Windt, "The Liar in the Prediction Paradox," Am Phil Q 10:65-8, 1973.
- A. Ayer, "On a Supposed Antinomy," Mind 82:125-6, 1973.
- M. Edman, "The Prediction Paradox," Theoria 40:166-75, 1974.
- J. McClelland & C. Chihara, "The Surprise Examination Paradox," J Phil Logic
- 4:71-89, 1975.
- C. Wright and A. Sudbury, "The Paradox of the Unexpected Examination,"
- Aust J Phil 55:41-58, 1977.
- I. Kvart, "The Paradox of the Surprise Examination," Logique et Analyse
- 337-344, 1978.
- R. Sorenson, "Recalcitrant Versions of the Prediction Paradox," Aust J Phil
- 69:355-62, 1982.
- D. Olin, "The Prediction Paradox Resolved," Phil Stud 44:225-33, 1983.
- R. Sorenson, "Conditional Blindspots and the Knowledge Squeeze: A Solution to
- the Prediction Paradox," Aust J Phil 62:126-35, 1984.
- C. Chihara, "Olin, Quine and the Surprise Examination," Phil Stud 47:191-9,
- 1985.
- R. Kirkham, "The Two Paradoxes of the Unexpected Hanging," Phil Stud
- 49:19-26, 1986.
- D. Olin, "The Prediction Paradox: Resolving Recalcitrant Variations," Aust J
- Phil 64:181-9, 1986.
- C. Janaway, "Knowing About Surprises: A Supposed Antinomy Revisited," Mind
- 98:391-410, 1989.
-
- -- tycchow@math.mit.edu.
-
- ==> logic/verger.p <==
- A very bright and sunny Day
- The Priest didst to the Verger say:
- "Last Monday met I strangers three
- None of which were known to Thee.
- I ask'd Them of Their Age combin'd
- which amounted twice to Thine!
- A Riddle now will I give Thee:
- Tell Me what Their Ages be!"
-
- So the Verger ask'd the Priest:
- "Give to Me a Clue at least!"
- "Keep Thy Mind and Ears awake,
- And see what Thou of this can make.
- Their Ages multiplied make plenty,
- Fifty and Ten Dozens Twenty."
-
- The Verger had a sleepless Night
- To try to get Their Ages right.
- "I almost found the Answer right.
- Please shed on it a little Light."
- "A little Clue I give to Thee,
- I'm older than all Strangers three."
- After but a little While
- The Verger answered with a Smile:
- "Inside my Head has rung a Bell.
- Now I know the answer well!"
-
-
- Now, the question is:
-
- How old is the PRIEST??
- ======
-
-