Mini Mysteries
(& Symbolic Arguments)
Use your knowledge of four common logical argument forms (Modus Ponens, Modus Tollens, Disjunctive Syllogism, Transitivity). Can you solve these very short mysteries?
Use your knowledge of four common logical argument forms (Modus Ponens, Modus Tollens, Disjunctive Syllogism, Transitivity). Can you solve these very short mysteries?
For reference, symbolic versions of the 4 common argument forms used in this mystery game are shown below. If you are not familiar with symbolic notation, you can find the English versions further below.
Modus Ponens | Modus Tollens | |
---|---|---|
p → q | p → q | |
p | ~q | |
q | ~p |
Disjunctive Syllogism | Transitivity (Hypothetical Syllogism) | |
---|---|---|
p ∨ q | p → q | |
~p | q → r | |
q | p → r |
Modus Ponens: Given the premises "if claim 1 then claim 2" and "claim 1", we can conclude "claim 2".
Example: "If I ate a sandwich, then I ate bread." "I ate a sandwich." Therefore, "I ate bread."
Modus Tollens: Given the premises "if claim 1 then claim 2" and "NOT claim 2", we can conclude "NOT claim 1".
Example: "If Timmy did his chores, then he is paid allowance" but "Timmy is not paid allowance." Therefore, "Timmy did not do his chores."
Disjunctive Syllogism: Given the premises "claim 1 or claim 2" and "NOT claim 1" then we can conclude "claim 2".
Example: "Today I went to work or I played video games" but "I did not go to work". Therefore, "I played video games."
Transitivity: Given the premises "If claim 1 then claim 2" and "if claim 2 then claim 3", we can chain these ideas together to conclude: "if claim 1 then claim 3".
Example: If today is Tuesday I go to work. If I go to work I eat salad for lunch. Therefore, if today is Tuesday I eat salad for lunch.
"You can point that six-shooter at me all you want," said the sheriff, "I just watched you shoot half a dozen people..."
( What does the sheriff say next? )
( What argument form would have this as its conclusion? )
( Solution will only show when all correct answers are chosen.)
"How do we know if we should arrest him?" asked the rookie, before knocking on the hotel room door.
"Listen," said Officer Hailey, "If he is here then he is violating his parole. If he is violating his parole then we arrest him. And so..."
( How should the rookie finish this argument? )
( What argument form lets him conclude this? )
Officer Melissa Jones was out on patrol when a house door swung open and a crazed man ran right up to her police cruiser.
He pointed back at another man who was standing in the open doorway, rolling his eyes. "Arrest him!" yelled the man by the cruiser, dramatically. "For... uh, murder! He murdered me!"
"Um," Officer Jones responded, unamused.
( What did she say next? )
( What argument could be used to support this? )
The district attorney spoke to the detective, "The DNA has come back, and it matches Mickey Farmay's DNA. We have spent this whole case proving that if it matches, then Mickey committed this crime."
(What do they conclude now?)
( What argument form lets then conclude this? )
After his students John and Rebecca had both entered his office, the professor stated, "I've brought you two here because your essays are identical. One of you copied the other. Since you two have never gotten along I can only assume that the one being copied had no idea."
John was quick to reply "She copied me!"
Since Rebecca had not copied John, she knew he was lying. Furthermore, she knew...
( What did she know? )
( How did she know this? )
"I wasn't even at that club yesterday!" cried Sam, the suspect.
"This should be quick," Mary thought to herself. She nodded towards the unusual blue dragon stamp on his hand.
"What, that?" he said nervously, "Oh, I got that the day before yesterday. The other witnesses must have gotten the day wrong."
Mary had already spoken to the club manager. They change their stamp every day, creating a brand new one each time. The first and only blue dragon they had ever used was yesterday.
( What does Mary conclude about yesterday?)
( What argument tells her this?)
"You have some nerve, standing right in front of my pistol," said Barney, "You know I always shoot as soon as I have an opportunity."
"That's all true," Will responded,
( What did Will say next? )
( What argument form does this follow from? )
The rookie walked up to Officer Hailey's desk, and begin speaking, "Remember Malakai, who started his 100% house arrest sentence this morning for dealing drugs to minors? Weed, PCP, LSD, meth... Anyway, we just pulled him over on Route 22, heading back toward the same neighborhood he used to deal from. What can we do?"
( How does Officer Hailey respond? )
( Which argument do we apply, before Modus Ponens
lets us conclude this? )
Rose and Jeremy sat on other ends of the remote cabin stared at each other, drenched in blood, and shivering.
"The killer must be one of us campers," Jeremy insisted, "We are hundreds of miles from civilization. The only people here are the ones that came in our group. We have to figure out which one is the killer."
"Everyone else is dead," Rose responded, closing her eyes, "I found each of their dead bodies, one by one." She looked back at Jeremy and proclaimed,
( What did Rose say? )
( What argument suggests this? )
Captain Marrix walked over the 6-inch deep snow in front of her deputy's house, feeling disappointed, not only for sullying the otherwise undisturbed white ground, but because she had a sinking feeling about what she was about to find. Her deputy, Jason, swung the door open. Captain Marrix looked down at the corpse next to the deputy's feet.
"I know this doesn't look good," Jason said, "You sent me home before the storm, but I swear I just got here! I hit some traffic on the way here, and then I had to pull over because the storm was so heavy I couldn't see the road, but then I couldn't even get the truck started again until the storm had completely passed."
"You walked in here and found her like this, and no one else?"
"Well yeah, on all counts. I mean we've had all the other doors and windows boarded up to prepare for the storm, so no one else could have gotten in or out without me noticing. The must have killed her and left a long time before I got here." Marrix did a quick search of the house to verify that there was no one else inside, and felt a rush of disappointment again when she found no one.
( Who does the captain suspect? )
( What argument form arouses this suspicion? )
Deputy: "Two bodies, each killed by a gunshot to the head. Only one was a suicide."
Chief: "Was the other an accident?"
Deputy: "We don't believe so."
( What did the Chief say next? )
( What might be the first premise to conclude this from Disjunctive Syllogism?)
Deputy: "Two bodies found, one in each of the house's two bedrooms, on opposite sides of the house. The victims were each killed by a gunshot to the head, by the exact same gun. Seems to be a murder-suicide. But we're not sure which happened first..."
Chief: "Come on..."
( What did the chief say next? )
( "The suicide happened first or the murder happened first"
would begin what argument form? )
Detective Charles Smith held the victim as the blood poured over her. Although he had not found the killer, he had traced the man down to this location, a possible childhood home. Smith believed this was the mother, but the blood loss had made her less than lucid. Nonetheless, he tried to use these last few moments of her life to extract a clue.
"All I need is his name," begged the detective, "What is his name?"
She just stared up at the sky and repeated over and over, "He has the same name as his father."
The detective sighed, "Okay..., well then, what was his father's name?"
"He... has the same name as his own father, the owner of this house." Those were her last words before dying in the detective's arms.
( What will the officer do? )
( What argument justifies this? )
Rodney smiled at his reflection calmly in the room's two-way mirror, as the officer played the surveillance footage from a recent robbery. The officer gave a comical and exaggerated smile, while staring into in a book labeled "County Prison Records", spinning a pair of handcuffs around on the table, and lightly singing some old song about a "chain gang". Rodney, who had been subject to various intimidation methods in the past, was unfazed by all of this.
"It's clear as day," said the officer finally said as the robber in the video smiled smugly at the camera, "That's definitely your face".
"You might think that's proof," laughed Rodney, "But that proves nothing. See, I have an identical twin- you can check the hospital records back in our hometown. And so, that just might be him in that video."
"And I'm sure you don't know where to find this twin of yours."
"As luck would have it, I don't." Rodney gave a facetious shrug, matching the officer's comical exaggeration. "We had a falling out a few years ago, haven't kept in touch. And even if we did, it'd be pretty hard to stick this on either of us. Maybe that's me, maybe it's him." He shrugged. "All that video proves is that it's one of us. That's all."
"No, you see, that wasn't a question. You say all the video proves is that it's one of you? Well... that's all it needs to prove. See?"
( What did the officer show him? )
( Now what argument could be used against the suspect? )
Joe walked up to the hotel desk clerk, showed his P.I. credentials and asked bluntly, "Do you know a woman by the name of Jamie Meren?" Jamie had been arrested this morning for a crime that had been committed on a date over 6 months ago. She felt she was being set up, and had used her only phone call to hire a private eye, Joe, who trusted the police about as little as she did.
"Um yeah," the clerk responded, "She's the morning clerk on weekends. Been here about a year."
"Can you describe her for me? Ever seen any signs of aggression, or even violence?"
"Ha! Honestly, she's kind of a goody-goody. She just received a Perfect Attendance Award for her first year, and employee of the month the past three months in a row. That's why we don't have to hire any more help for Saturday or Sunday mornings - she handles everything all by herself." He pointed to the wall behind him, which hosted the attendance award plaque and the Employee of the Month picture, next to a loudly ticking analog clock and a wall calendar flaunting the current month's bikini model (which made Joe snicker at its oddity, since it was the middle of December).
"Is that time right?" he asked, and when the clerk raised his eyebrow, explained "I don't carry a cell phone. I don't really like having a government-tracked device in my pocket."
The clerk gave Joe an unexpected nod of agreement. "Same here. I assume it's right but our computers are down, so I'm not 100% sure."
Joe's eyes roamed up to a small security camera up in the corner. "Does that camera work?"
"I mean... it does... records 24-7 and the videos are saved to the cloud somewhere. I tried to find a tape once when someone said he checked out earlier than he really did. Eventually I just gave up because the storage system is such a mess. I refunded his money."
"I know how to prove she's innocent. I don't want to go through the trouble of looking through the video storage system unless I know for sure it will show her."
( What can he check to quickly determine if he would see Jamie on the tapes? )
( What argument suggests this? )
When detectives Ray Jones and Maya Glan interrogated Felix Smith about a murder at their neighbor's house, he swore he was being set up by his wife Tammy. He claimed he was at home watching their toddler, Junior, all day. Tammy did this most days while Ray worked on his computer from home, but because of the block-wide power outage that had left them with no electricity for the past week, he offered to watch Junior while she went shopping.
It was after she had left that stories began to diverge. Felix said he didn't know what Tammy had been up to today, but it sounded like nothing good. When the detectives interrogated Tammy about her whereabouts today, she basically said the same thing about Felix.
"I went to the festival uptown early in the morning, and when I walked back in around noon, Felix was stomping around angrily, like he was plotting something. I was so frightened that I dropped the groceries all over the floor." She pointed down to the bags scattered around. Junior stomped around, and Maya couldn't decide if she believed he was emulating his father, or just trying to figure out how to walk. "I must have passed out in fear, and didn't wake up until you rang the doorbell. Who knows what Felix could have done during those 5 hours."
"You're sweating," said Maya, "Nervous about anything?"
"No no," Tammy said, pointing to a bead of sweat on Maya's own arm, "I mean it's warm in here. We don't have air conditioning. We use electric fans, but the stupid power outage..."
Junior tripped and fell flat on his face. Ray tried not to laugh. Junior begin crying and Maya almost wanted to cry herself from the piercing sound. "Oh, poor boy," said Tammy, "He's so awkward and clumsy, just like his father." She picked him up and sat him in his high chair, then reached into one of the grocery bags on the floor. "All you gotta do is give him something sweet, and he'll forget all about it. Just like his father." She winked at Ray.
"Um, so..." Ray said shyly, "You had time to go to the festival and get back before noon? Why not just go to the store down the streen?"
"Oh, he's allergic to cow's milk," Tammy explained, nodding towards Junior, "But it's his birthday! I had heard about a kiosk there that sells cake and ice cream made with almond milk." She opened the carton of ice cream and handed it to Junior with a thick plastic spoon decorated with the company's logo, an anthropomorphic almond in a top hat and a pink bowtie.
Junior shoved his spoon down into the ice cream and it snapped in half, causing him to cry again. Maya was getting frustrated. Tammy reached into the silverware drawer and gave Junior a stronger, metal spoon.
Someone was lying, and Maya knew who.
( Who was lying? )
( Which argument type helped her deduce this? )
The crime consultant walked into the victim's house, putting his gloves on, and yelled upstairs to the suspicious captain, who was looking over the crime scene alone. "Just us so far, huh? Have you called for ballistics or checked for gun powder residue?"
"No, I just called it in a few minutes ago. How were there no witnesses to this?"
"I assume there are no witnesses because this house in the middle of nowhere," the consultant laughed, as he walked up the stairs and then down the hall toward the room. The house was indeed in a rather remote area, and in fact the only reason the captain had come here was to check in on a person of interest who had escaped from a recent attack by a man in a mask and gloves. Now the captain had found the woman dead, with a single bullet wound in her chest, and he instantly regretted giving in to her wish to have no patrol cars watching the house.
"And yet here we are," called the captain, looking down at the victim's otherwise pristine blouse, "I had a sneaking suspicion about this one, so I just called it in now, a 'Brutal stabbing to the gut. No witnesses.' And yet here we are." They could hear the sirens approaching.
( Who killed the woman? )
( What was the murder weapon? )
"So you believe this was an accident?" Detective Amber Neilson looked at Ms. Vernon suspiciously, after noticing what were clear signs of a struggle.
"Yes, of course," Ms. Vernon answered, "I heard something like footsteps coming from inside the room around 4:05pm, even though Papa was supposed to be sleeping, and when I came to tell him to stay in bed, I heard him yell 'Woah' like he was starting to trip. I mean, the door and walls are thick, so the sound was a little muffled, but it definitely sounded like 'Woah' or 'Oh' or some sound of distress, you know? He must have fallen and hit his head exactly as I opened the door, because I didn't really hear the fall."
Amber looked out the window at the garden filling the side of the house. She noticed a water droplet falling off a sunflower by the window, and then a large damp spot on the carpet just inside the window. "Why is the window open?" she asked, "Wasn't it raining earlier?"
"Yes, hm. After the rain stopped, Juniper must have opened it to give Papa some air. Oh, Juniper is our, well... he's a clown by trade..." Ms. Vernon gave a sligh chuckle of embarrassment as Amber raised her eyebrows. "But he specializes in taking care of senior citizens. He works from 3 to 4 every Friday, while I go grocery shopping. Yes, I remember now. I had just gotten home when he was on his way out. I was about to offer him an umbrella as he left, when I noticed the rain had just stopped." She reached into a desk drawer and handed Amber a business card:
Juniper, Professional Clown and Caretaker
Magic, juggling,
celebrity impressions (modern and classic eras),
ventriloquism & balloon animals
It had a full-body photograph of Juniper in full clown getup: the white makeup, the red nose, the outrageously oversized shoes, the polka-dot onesie. "This is what he wears to take care of senior citizens?" Amber asked.
"Yup, exactly that. Papa loved it. Juniper says the onesie and shoes need special tools to get on or off- which can take over an hour- but that it's worth it to see Papa's face light up at the sight."
"Well it's not very lit up anymore," Amber thought crudely to herself, looking down at the corpse. She knew exactly where she wanted to investigate. Within a few minutes, she was whispering to herself, "Gotcha."
( Where did Amber find the evidence? )
( What did this evidence confirm?)
Congratulations! You figured out all of the mini mysteries, and identified the correct logical argument forms to solve them.
Well done, detective!