Logical ReasoningDifficulty: Hard

PT118 S3 Q11 Explanation

Biologist: Humans have five fingers

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

TopicsStrengthen

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Stimulus

Biologist: Humans have five fingers because we descended from a fish with five phalanges in its fins. Despite our prejudices to the contrary, our configuration of fingers is no more or less useful than several other possible configurations, e.g., six per hand. So, if humans had descended from a fish with six hand, then we would be just as content with that configuration.

What this question is testing

Strengthen

Your task

Find the choice that makes the argument's conclusion more likely to be true.

Common trap

Answers that are consistent with the argument but add no real support, or that strengthen a claim the argument doesn't make.

Winning move

Locate the gap between evidence and conclusion, then pick the choice that closes it.

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

The question
11.

Which one of the following, if true, most strengthens the

Answer choices

  1. No Impact7% picked this

    Everyone is equally content with our present configuration

    We don't care whether we're currently equally content or currently content to wavering degrees. The conclusion we're judging is about whether our current contentment (however it's distributed) would be matched in a 6-fingered world.

  2. Inverted Logic3% picked this

    Humans are never equally content with two things of

    They flipped the illegal lightswitch on this one. We wanted: if it's equally useful ? we're equally content (prem) (conc) And this is giving us if two things are ? we're not equally content not equally useful

  3. Correct65% picked this

    Humans are always equally content with two things of

    Why this is right

    To match the move from Premise to Conclusion, we wanted: if it's equally useful ? we're equally content (prem) (conc) And this is giving us exactly that. If anyone was nervous that it was "too strong", that's the opposite of what we worry about. On Strengthen, Weaken, Paradox, Principle-Justify, and Sufficient Assumption, there's no such thing as too strong. We would only ever worry if something were too weak. Those question stems ask us to pretend this answer is true ... hypothetically, if it were true, which would have the most impact? if valid Which of the following, if true , most .... if assumed

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

  4. Inference, Not A New Idea24% picked this

    The perceived usefulness of our configuration of fingers is an illusory result

    This sounds like an Inference we can pull out of the premises, so it doesn't seem to provide us with anything we didn't already have. We've already accepted that 6-fingered and 5-fingered would be equally useful, because we concede the truth of the premises (99.5% of the time). This answer doesn't address the argument's gaping vulnerability -- what if our contentment is based on more than just usefulness?

  5. Trap1% picked this

    At least one species of fish had six phalanges in

    No Impact Deal with Trigger, Not Outcome Whenever you have a conditional conclusion, like If Barack Obama started acting in movies, he would be one of Hollywood's top actors you get no Strengthening or Weakening value out of addressing the trigger. This author isn't suggesting that Obama is even 1% likely to start acting in movies. She's just making a hypothetical conclusion, which you're totally allowed to do. We accept the "if" part of any conditional conclusion, as though it's a Premise already baked in. The only way to argue with this claim is to put yourself in a world where Obama now acts in movies, and try to argue that he wouldn't be one of Hollywood's top actors. Since this answer choice is trying to add some credence to the hypothetical idea of "if we had come from 6-phalanged fish", it has no value whatsoever.

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