Support All intelligent people are nearsighted. █ ██ ████ ████████████ ██ █ ████ ██ █ ███████
Notice that the question stem flags two logical flaws in the stimulus. This is unusual.
Let’s start with a formal logic representation of the argument:
P1: Intelligent → Nearsighted
P2: MeVery Nearsighted
________
Con: MeVery Intelligent
(Note: we’re treating “Genius” as “Very Intelligent” here.)
First, this argument confuses necessity for sufficiency by affirming the necessary condition (Nearsighted) and concluding the sufficient condition (Intelligent) must be true. This pattern of flawed reasoning is common enough that you should aspire to recognize it by name when you see it.
Second, this argument treats a categorical claim (all intelligent people are nearsighted) as though it’s a correlational claim (the more intelligent you are, the more nearsighted you are). This flaw isn’t as common as the first one. Knowing the precise terms is nice, but as long as you’ve spotted something along these lines, it’s okay if you can’t put it into words.
Which one of the following ████████ ████ ██ ███ ███████ █████ █████████ ██ ███ ████████ ██████
I must be ██████ ███████ ███ ███████████ ██████ ███ ███████████ ███ █ ████ ███████ █████████
(A) dies when it negates the necessary condition (instead of affirming it) and concludes the sufficient condition must not be true (instead of must be true). Here’s some formal logic:
P1: Intelligent → Nearsighted
P2: Me/Nearsighted
________
Con: Me/Intelligent
Perhaps (A) does preserve the categorical / correlational flaw if you treat “perfect eyesight” as “very not nearsighted” and you treat “stupid” as “very not intelligent,” but the necessary / sufficient mismatches are much easier to assess.
All chickens have ██████ ████ ████ ███ █ █████ ██ ████ ████ ████ ██ █ ████████
(B) doesn’t preserve the categorical / correlational claims flaw. To preserve the flaw, (B) would need to jump from chicken to like…ultrachicken. Like this bird has one hell of a beak, so it must be one hell of a chicken.
(B) does affirm the necessary condition, though. Here’s the formal logic:
P1: Chicken → Beak
P2: BirdBeak
________
Con: BirdChicken
All pigs have ████ █████ ███ ████ ██████ ███ █████ █████ ██ ████ ██████ ████ ██ █████ ██ ███ ██ ███ ████
(C) is a flawed argument for sure, but even without parsing it all out it should strike you as too dissimilar to the stimulus to even take seriously. Ideally you’d dismiss (C) on your shallow dip, never to return.
I guess the logic looks like this:
P1: All pigs = 4 legs
P2: This spider = 8 legs
P3: 8 is two times as big as 4.
________
Con: This spider is two times as big as all pigs.
I find this argument hilarious, but it certainly doesn’t preserve either flaw.
John is extremely ██████ ██ ██ ████ ██ █████████ ████ ███████ ███ ████ ██████ ███ ██████
(D) preserves both flaws. It affirms the necessary condition (Happy) and concludes the sufficient condition (Tall) must be true. It also treats a categorical claim (all tall people are happy) as though it’s a correlational claim (the taller you are, the happier you are). Here’s the formal logic:
P1: Tall → Happy
P2: JohnVery Happy
________
Con: JohnVery Tall
All geniuses are ████ ████████████ █ ████ ██ ████ ███████████ █████ █ ██ █ ███████
(E) should immediately strike you as suspicious because its subject matter is so similar to the stimulus. Only the structure matters in these questions, so answer choices that preserve substance are usually trying to bait you.
Speaking technically, (E) is mainly wrong because it affirms the sufficient condition (Genius) instead of the necessary condition (Nearsighted).
The categorical / correlational dynamic is a bit off as well – the jump from intelligent to genius is missing – but the necessary / sufficient mismatch is much easier to assess.
Here’s the formal logic:
P1: Genius → Nearsighted
P2: MeGenius
________
Con: MeVery Nearsighted