Maybe I’m wrong. Maybe I’m not. And I don’t mean to pick on Marilyn vos Savant, who is almost always interesting and accurate, and never claims a record IQ brings infallibility. But I think today’s answer to a puzzle is flawed, because two answers can be right.
Here’s the puzzle:
When a prominent psychiatrist was found slimed, police questioned four patients who saw him that day. They met and decided that every statement would be a lie.
Avery said: None of us slimed the doctor. He was clean when I left.
Blake said: I arrived second. The guy already was a mess.
Carlo said: I arrived third. He was clean when I left.
David said: The evildoer arrived before me. The doctor already was a mess.
Who slimed the psychiatrist?
Stop and solve it yourself if you like, then read on.
Basically, here’s the logic: Two men said the doctor was “already a mess” when they arrived, which means (these statements being lies) he had to be clean when the second man arrived. Two other men said the doctor was clean when they left, which means he’d been slimed before the third man left. But that’s all we can tell. So we can’t tell if the second man did it, or the third.
Check out Parade.com’s explanation for the so-called “correct” answer. But the reasoning is flawed, because it concludes that David’s saying “The evildoer arrived before me” can only mean, since he’s lying, that “7) The evildoer arrived after David.” Au contraire. It means EITHER he arrived after OR David did it. The order given seems correct — Blake, David, Avery, Carlo — but I’m thinking we lack enough information to be sure whether patient No. 2 or 3 — David or Avery — did it.
The proof lies in supposing David did it then re-reading all the statements.
He said, “The evildoer arrived before me. The doctor was already a mess.” That’s a lie if he did it. Avery said: “He was clean when I left.” That’s works, too, since Avery was third. Carlo, fourth, said, “He was clean when I left.” Blake, really first, said, “The guy was already a mess.” Lies, all lies.
Or examine this logic from the magazine: “David got there next and found the doctor clean, so Blake was not the bad guy.” Huh? That doesn’t follow, since the bad guy would have to find the doctor clean, before sliming him, right?
I’m not saying Avery couldn’t have done it. He could have. But so could David.
Am I missing something? Or did vos Savant and her editors?
A previous post puzzle lovers might enjoy: How to Solve Life’s Picture Puzzle in Seconds.