Logical ReasoningDifficulty: Hard

PT144 S2 Q21 Explanation

Although the first humans came to

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

TopicsParallel Flaw

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Stimulus

Although the first humans came to Australia 56,000 years ago and undoubtedly brought new diseases with them, human-borne diseases probably did not cause the mass extinction of large land animals and birds that took place over the following 10,000 years. After all, more than 55 different species disappeared at about could be fatal to animals across that many different species.

What this question is testing

Parallel Flaw

Your task

Break the argument into its conclusion and evidence, then do exactly what the question stem asks with that structure.

Common trap

Answers that sound relevant to the topic but don't connect to the argument's actual reasoning.

Winning move

Predict what a right answer must do, then test each choice against the conclusion-evidence 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
21.

Which one of the following arguments exhibits flawed reasoning that is most parallel to that in

Answer choices

  1. No Part/Whole Relationship23% picked this

    Even though high interest rates can lead to an economic downturn, high interest rates probably did not cause the current economic downturn. It is

    The conclusion is correctly anti-causal sounding - high interest rates probably didn't cause the economic downturn. But to match the original argument, we'd need a premise saying "After all, no single interest rate could ever cause an economic downturn."

  2. Correct39% picked this

    Even though I can fix some things and you can fix some things, the two of us will be unable to repair our apartment

    Why this is right

    This is drifting a lot from the original, but it's still our closest match for Part vs. Whole. It's vulnerable to a similar objection we used with the original argument — even though no single disease alone could kill all those species, a bunch of diseases together could have killed al those species. Here we'd be saying — even though neither person alone can repair the apartment, the two of them together could repair it.

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

  3. Bad Conclusion Match25% picked this

    Even though Lena, Jen, and Mark would like to go out to dinner together after the movie tonight, they will probably go straight home

    A similar Part to Whole flaw would take a premise like, no single restaurant is liked by all three of them and then conclude restaurants aren't liked by all three of them This argument's conclusion (probably go home) is not recycling an idea from the premise. In the original argument and in correct answer (B), an idea from the conclusion (did not cause 55 extinctions / cannot repair whole apartment) shows up in the premise too. The argument didn't say, "Since each of the three people are likely to go straight home, it is likely that all three of them will go straight home."

  4. Bad Conclusion Match12% picked this

    Even though this painting is highly regarded by critics, it cannot legitimately be deemed great art. Most art that was produced in the last

    The conclusion of the original argument and the correct answer is about a group of things. This argument's conclusion is about one thing: this painting. The flaw in this argument is assuming that "Because most X's are Y, this specific X must be a Y."

  5. No Part/Whole Relationship2% picked this

    Even though the influenza vaccine does not always prevent influenza, it sometimes reduces the severity of its symptoms. Therefore it is incorrect to say

    This argument is just discussing whether the flu vaccine means you get no flu, a reduced flu, or you still get the flu. There's nothing like "no single vaccine can X" or "no single person who gets the vaccine is X".

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