Logical Reasoning

PT154 · S2 · Q19 Doctor: The patient had been

A free, expert breakdown of this official LSAT Logical Reasoning question.

Save & drill this skill — build targeted practice sets from questions like this one
Video walkthroughs — watch every question solved step by step
81 official LSATs — as questions, timed sections & full-length tests

Start practicing free

Doctor: The patient had been experiencing back and leg pain.

Conclusion (conclude / therefore)

The pressure on the nerve in question was causing this patient's back/leg pain.

Evidence

A computer scan suggested there was pressure on a nerve going from the lower vertebra to the leg.

This type of pressure can cause inflammation, which can cause pain.

If the nerve was inflamed, cortisone would reduce the inflammation. We injected cortisone and then the patient experienced pain relief.

Evaluate

Since the doctor is trying to Solve the Causal Mystery of this patient's nerve/back pain, we could use our Curious Fact / Explanation mindset.

The doctor is trying to explain the curious back/leg pain and explains it via pressure on the nerve in question. So we would worry about Alternate Explanations for the back/leg pain and we would worry about the plausibility of the doctor's diagnosis.

The most important moment to notice is when the doctor introduces a conditional claim:

if the nerve was inflamed, cortisone would help. Cortisone helped. Thus, the nerve was inflamed.

What's wrong with that mini-argument?

Well, that's an illegal reversal of course. Just because cortisone helped doesn't show that the doctor's diagnosis was correct.

Perhaps there are other possible causes for which cortisone would also help. We haven't ruled out any of those possibilities.

Goal

Look for an answer saying something necessary to the internal logic of the doctor's diagnosis, or look for an answer ruling out the possibility of an alternate diagnosis.

19.

Which one of the following is an assumption required by the doctor's argument?

Computerized scans are the most
Too Strong: most accurate
The word "most" is wrong 99% of the time we see it in Necessary Assumption. The doctor is definitely assuming that computerize scans can provide accurate diagnoses. There's no reason she needs to assume it's the #1 most accurate way. If it were the #2 most accurate way, her argument wouldn't be changed.
3% picked this
The cortisone injection did not
Opposite, if anything
When we see a Necessary Assumption answer choice ruling out an idea with the word "not", we get enticed. We want to negate these and see if they turn into an objection. Would this negation weaken? the cortisone shot did reduce pressure on the inflamed nerve in the leg? That doesn't sound like a weakener at all to me. The doctor is perfectly happy believing the cortisone shot reduced inflammation AND reduced pressure on the nerve (in fact, reducing inflammation is, I believe, meant to reduce pressure). Since the negation might even strengthen, this answer can't be right.
8% picked this
Correct
The pain relief did not
Why this is right
When we see a Necessary Assumption answer choice ruling out an idea with the word "not", we get enticed. We want to negate these and see if they turn into an objection. Would this negation weaken? the pain relief did occur merely through the placebo effect Sure, that weakens. That provides an alternate cause. It's not saying "in addition to the therapeutic value of the cortisone shot, the patient also got a placebo effect." It's saying, "The pain relief was merely from / purely from the patient's psychological state." Who knows whether the root cause of the pain was ever a pressured nerve. The author's evidence for that included the fact that a cortisone shot provided relief (and a cortisone shot is a treatment for the supposed problem). But this negation is saying, "the cortisone shot did not provide relief. The placebo effect did", so that badly weakens the author's signature piece of evidence in favor of her diagnosis.
Skill tested: Necessary Assumption · how this choice captures the argument's function is the move to repeat next time.
69% picked this
Only cortisone injections can cause
Too Strong
Too Strong: only Only Thing Mentioned ? Only Thing The author doesn't need to assume such an extreme claim that "ONLY cortisone shots reduce inflammation". This is just doing an age ol' trick on Necessary Assumption, where they try to make students think that the only thing of a certain type that was mentioned is therefore the only thing of that type. Like if an author says "French cheese is delicious", there will be a trap answer accusing him of thinking, "only French cheese is delicious".
10% picked this
The best treatment for back
Too Strong: best / usually
We have another massively overstated answer choice here. The author assumed that a drug (cortisone) that relieves inflammation would be a treatment for this dude's inflammation. She doesn't need to assume that more than 50% of the time it's the #1 anti-inflammation option. If it were only the #1 option 49% of the time, that's plenty good. If it's the #2 option 100% of the time, that's plenty good.
10% picked this

Continue the review in LSAT Lab

Save this question, watch the video walkthrough, and drill similar questions in your LSAT Lab account.

Save and practice this skill

LSAT Lab

Turn this review into a targeted study plan.

Save this question, drill more like it, watch the video walkthrough, and track your progress in your LSAT Lab account.

Start practicing free