Self-study
Support Jack's dog howls whenever a train goes by. ████████████ █ █████ ████ ██ █████ ████ ██ ███████ ███ ████ ██ ██████ ███ ████ █████████ ████ █████ ██ ██ ███████ ███
Objective: Parallel Questions
Parallel questions have a highly regimented theory and approach – even if your core logical intuitions are very strong, following a routine process specifically built around the LSAT’s unique patterns will dramatically reduce the time and mental energy required to identify the correct answer. So review these lessons. They’re important.
In short, though, our approach will be to develop an abstract model of the stimulus’ argument, preserving the structure but not the subject matter, then take a shallow dip into the answer choices looking for structural mismatches. Usually that suffices to identify the correct answer, but sometimes we’ll need a deep dive to distinguish between the (usually just two) answer choices that remain after our shallow dip.
First: Core Skills
This question hinges on a short list of formal logic skills. Let’s lay them out on the table right now.
1: Whenever indicates a sufficient condition.
In every single answer choice, Premise 1 is worded in a simple “[All/Most/Some] Serious joggers can benefit from good running shoes” structure. Serious joggers comes first in both the sentence and the diagram.
Serious → Benefit
In the stimulus, Premise 1 is worded in the opposite way: “Jack’s dog howls whenever a train goes by.” Howls comes first, but it’s second in the diagram because the word “whenever” indicates a sufficient condition regardless of where in the sentence it appears.
Train → Howls
So Premise 1 looks different than its counterparts in the answer choices, but logically it matches up (except in (B) and (D), which are a “most” and a “some” claim, respectively).
2: “Some” claims are reversible.
The nature of the “some” relationship allows us to swap the terms around and retain its meaning: if some cats are pets, some pets are cats
Cats ←some→ Pets
Pets ←some→ Cats
Recognizing you can flip the wording of “some” claims is also critical to success in this question.
3: There’s only one way to draw an inference from a “some” claim
If you’re rusty on your valid formal arguments, now’s a great time to review. The only valid way to derive an inference from a “some” claim is to put some before all.
Pets ←some→ Cats → Conniving
validly gives you…
Pets ←some→ Conniving
Nothing else works.
Distilling The Argument’s Structure
Get ready to use all those skills, baby! Let’s diagram the argument. Here’s how it looks on a first translation from the English:
Premise 1 : Train → Howls
Premise 2 : Train ←some→ Wash
________
Conclusion : Wash ←some→ Howls
This argument works by putting some before all, but you have to make a few adjustments to see it clearly. Let’s swap the order of Premise 2’s terms and put it first:
Premise 2: Wash ←some→ Train
Premise 1: Train → Howls
________
Conclusion: Wash ←some→ Howls
There we go. If you like a nice pretty chain, it’s easy to make now:
Premise 1+2: Wash ←some→ Train → Howls
Our correct answer choice needs be a valid argument that puts some before all.
18.
The pattern of reasoning in █████ ███ ██ ███ █████████ █████████ ██ ████ ███████ ██ ████ ██ ███ ████████ ██████
a
Every serious jogger ███ ███████ ████ ████ ███████ ██████ ███ █████ ████ ██ █ ███ ███████ ███████ ███ ██████ ██ ███ ██ ████████ █████████ █████ ████ ██████ ███ ███ ███████ ████ ████ ███████ █████ ██████ ██ ███ ██ ████████ █████████
(A) does a lot to mirror the wording of our stimulus, but it subtly swaps Premise 2 and the Conclusion.
(A) starts off by giving us an “all” claim, just like our stimulus. So far so good.
P1: Serious → Benefit
You might think (A)’s second sentence looks pretty good too. It links P1’s sufficient condition to a new concept, which is exactly what Premise 2 in our stimulus does.
P2?: Serious ←some→ Ordinary
But (A)’s second sentence isn’t a premise – it’s the conclusion. (A)’s actual diagram looks like this:
P1: Serious → Benefit
P2: Ordinary ←some→ Benefit
________
Con: Serious ←some→ Ordinary
This diagram asks us to put all before some:
P1+P2: Serious → Benefit ←some→ Ordinary
b
Most serious joggers ███ ███████ ████ ████ ███████ ██████ ███ ████ ███████ ███████ ██████ ██ ███ ██ ████████ █████████ ██ ████ ██████ ███ ██████ ██ ███ ██ ████████ ████████ ███ ███████ ████ ████ ███████ ██████
(B) starts with a “most” claim BOOO GET OUT OF HERE (B) BOOO!!!
Here’s (B)’s diagram:
P1: Serious –most→ Benefit
P2: Serious ←some→ Ordinary
________
Con: Ordinary ←some→ Benefit
If putting some before most were a thing, (B) would… still be wrong because most =/= all.
c
Any serious jogger ███ ███████ ████ ████ ███████ ██████ ███ █ ███ ███████ ███████ ██████ ██ ███ ██ ████████ █████████ ██ ████ ██████ ███ ███ ███████ ████ ████ ███████ █████ ██████ ██ ███ ██ ████████ █████████
(C)’s premises and conclusion are conveniently presented in the same order as our stimulus. They didn’t have to do that – very sweet of them.
As mentioned, the terms in Premise 1 are presented in the opposite order between the stimulus and (C), but that doesn’t matter because they’re logically equivalent. Here’s (C)’s diagram:
P1: Serious → Benefit
P2: Serious ←some→ Ordinary
________
Con: Benefit ←some→ Ordinary
Let’s reverse Premise 2 and put it first, just like we did for the stimulus:
P2: Ordinary ←some→ Serious
P1: Serious → Benefit
________
Con: Benefit ←some→ Ordinary
Wonderful, we’ve put some before all. Look at the pretty chain:
P1+P2: Ordinary ←some→ Serious → Benefit
d
At least some ███████ ███████ ███ ███████ ████ ████ ███████ ██████ ███ █████ ███ ███████ ███████ ███ ██████ ██ ███ ██ ████████ █████████ ██ ████ ██████ ███ ██████ ██ ███ ██ ████████ ████████ ███ ███████ ████ ████ ███████ ██████
(D) starts with a “some” claim BOOO GET OUT OF HERE wait a sec it might just be that (D) is presenting the premises and conclusion in a different order. Let’s look at the other sentences.
TWO MORE “SOME” CLAIMS?!? BOOO GET OUT OF HERE (D) BOOO!!!
Here’s (D)’s diagram:
P1: Serious ←some→ Benefit
P2: Serious ←some→ Ordinary
________
Con: Ordinary ←some→ Benefit
You can’t put some before some that is no good at all.
e
Any serious jogger ███ ███████ ████ ████ ███████ ██████ ███ ████ ███████ ███████ ████████████ ██████ ██ ███ ██ ████████ █████████ ██ ██████ ███ ███ ███████ ████ ████ ███████ █████ ████████████ ███████ ██ ███ ██ ████████ █████████
(E) combines an “all” claim with a “some” claim to derive an “all” claim conclusion. It’s otherwise a good match.
(E) starts off by giving us an “all” claim, just like our stimulus. So far so good.
P1: Serious → Benefit
It then presents a “some” claim linking P1’s sufficient condition to a new concept, which is exactly what Premise 2 in our stimulus does. Unlike answer choice (A), this claim is also a Premise. So far so good, then.
P2: Serious ←some→ Ordinary
The problem comes in the conclusion: “anyone who can benefit from…” and (E) is dead. Here’s the full diagram:
P1: Serious → Benefit
P2: Serious ←some→ Ordinary
________
Con: Benefit → Ordinary