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The Rock of Truth
The little woman sitting in front of Samuel was peddling her wares with an attitude that screamed “I am doing you a favour by selling you this". An attitude, he later learned, characteristic of those Endirian merchants you should trust the least.
So far, nothing she showed had caught his attention, and she appeared to pick up on that. She was packing most of her belongings, almost ready to go, and then...
“Oh, I almost forgot,” she said. “I do have one more thing you might be interested in.”
The Endirian removed a small box from her bags and opened it to reveal a green rock.
“What's this?”
“This, my good sir, is a rock of truth,” the merchant said. “It's a wonderful device”
“And what does it do?” Samuel asked.
“Well, if someone tells a lie and touches the rock, it will glow” she replied. “I'd love to give you a demonstration, but it takes two hours for the rock to charge and I have urgent business”
“Tell you what,” she continued, “for a quarter of the full price, you can try out the rock for yourself over the weekend”
“Lady, we have a deal”
Samuel and the Endirian signed a contract which stated, basically, that the merchant would return Sam's money should the rock be faulty, and Sam would pay the full price if it worked as described. Sam was now 200 cred poorer, but feeling like had cheated a genie out of a fourth wish.
* * *
“Your piece of shit rock is broken!”, Samuel yelled.
“Is that so?”
As a reply, Sam placed the rock on the table, said 'My name is Samuel Norten' and then touched the rock. It glowed brightly. He then declared 'My name is not Samuel Norten' and touched the rock, to the same effect.
“I don't see the problem,” the merchant said. “It glowed, did it not?”
“It glows whenever I touch it! What use do I have for the rock if it doesn't help me tell who's lying?”, he ranted.
“I'm afraid I never promised you a lie detector, Mr. Norten. All I said was that the rock would glow when touched after saying a lie, which it does. What the rock does in any other circumst-”
Sam, as it turned out, was not in the mood for such technicalities, something he manifested by literally throwing the Endirian out of his house. She later sued him for assault and breach of contract, though the result of the latter trial left her with a very poor opinion of the teaching of logic in the local education system.
A short one I wrote during my vacation, inspired by, um, looking at rocks lying on the coast of lakes. Those didn't glow in any circumstances, as far as I know.
ReplyDeleteFor the sake of babbling about material conditionals: In logic, an "if p then q" statement is only considered false if p happens and q does not. If q (the rock glows) is true, it doesn't matter whether p (someone lied before touching) is true or not. "If p then q" guarantees that q will be true when p is true, but says nothing about what will happen when p is false.
What Sam interpreted here is called a biconditional, usually phrased as "p if and only if q". In a biconditional, p and q are always both true or both false, that is if p is true then q will be true, and if p is false then q will be false. Sam thought the rock would glow if the person touched it had lied, and that it would not if the person touching it hadn't lied. The last was an unsupported assumption if you take the Endirian's words as a strict logical statement, which is not usually something you should do with people's words unless you enjoy pissing them off. I know from experience most people don't find that as hilarious as I do.