Logical ReasoningDifficulty: Hard

PT106 S2 Q22 Explanation

Wirth: All efforts to identify a gene

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

TopicsFlaw

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Full official LSAT questions are available through LawHub. This page provides LSAT Lab's explanation, strategy, and review tools without republishing the full official question.

Stimulus

Wirth: All efforts to identify a gene responsible for predisposing people to manic-depression have failed. In fact, nearly all researchers now agree that there is no “manic-depression gene.” Therefore, if these researchers are right, genetically predisposed to manic-depression is simply false.

Chang: I do not dispute your evidence, but I take issue with your conclusion. Many of the researchers you refer to have found evidence that a set of several genes is involved genes produce a predisposition to manic-depression.

What this question is testing

Flaw

Your task

Describe the reasoning error the argument actually commits.

Common trap

Answers that name a real logical flaw the argument doesn't actually make.

Winning move

Articulate the gap in the reasoning yourself, then match it to the choice that describes that gap.

Reading along? Open the full official question in LawHub — we show a fragment here and keep the reasoning in our own words.

The question
22.

Which one of the following most accurately expresses Chang’s criticism of

Answer choices

  1. Correct67% picked this

    It presupposes only one possibility where more than

    Why this is right

    We can make this work. Wirth is assuming that genetic predispositions only come from a single gene, and Chang is saying "it's also possible that genetic predispositions come from a cluster of genes interacting".

    Skill tested: Flaw · how this choice captures the argument's function is the move to repeat next time.

  2. No Contradiction12% picked this

    It depends on separate pieces of evidence that contradict

    Chang (and pretty much every LSAT author ever) does not accuse the other person of saying contradictory things.

  3. Unsupported: outside their expertise0% picked this

    It relies on the opinion of experts in an area outside the experts’

    We are inclined to think that the experts we're hearing about are experts in the field of searching for genetic underpinnings to diseases. We have no reason to think otherwise, and Chang doesn't say anything to that effect. He implicitly is trusting the researchers they're talking about.

  4. Too Strong: disallows all counterevidence12% picked this

    It disallows in principle any evidence that would disconfirm

    This is one way to describe circular reasoning: being so convinced by the truth of your conclusion that you fail to consider counterevidence. Chang does not imply that Wirth is being this stubborn or narrow-minded.

  5. Out of Scope: unlikely vs. impossible9% picked this

    It treats something that is merely unlikely as though it

    Nothing Chang says is a commentary on Wirth going too far with strength of language. Chang isn't saying, as this answer implies, that "Yes it's unlikely that there isn't a genetic predisposition, but it isn't certain!" Chang is saying, "It actually looks like there is a genetic predisposition, only it comes from a set of genes, not a single gene."

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