Logical ReasoningDifficulty: Hard

PT131 S1 Q15 Explanation

The typological theory of species

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

TopicsFlaw

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Stimulus

The typological theory of species classification, which has few adherents today, distinguishes species solely on the basis of observable physical characteristics, such as plumage color, adult size, or dental structure. However, there are many so-called "sibling species," which are indistinguishable on the basis of their appearance but cannot interbreed and thus, according theory does not count sibling species as separate species, it is unacceptable.

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
15.

The reasoning in the argument is most vulnerable to criticism on the

Answer choices

  1. Not a Flaw2% picked this

    the argument does not evaluate all aspects of the

    In order to undermine the typological theory, the argument does not need to evaluate all aspects of the typological theory, but rather those aspects which are wrong.

  2. Wrong Flaw8% picked this

    the argument confuses a necessary condition for species distinction with a sufficient condition

    This common LSAT flaw is not present in this argument. This reasoning structure is not conditional logic, but rather comparison.

  3. Correct45% picked this

    the argument, in its attempt to refute one theory of species classification, presupposes the truth

    Why this is right

    This presents an assumption of the argument.

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

  4. Not a Flaw44% picked this

    the argument takes a single fact that is incompatible with a theory as enough to show that

    A single fact that is incompatible with a theory is enough to show that theory to be false.

  5. Not a Flaw1% picked this

    the argument does not explain why sibling species

    The argument does not need to explain why sibling species cannot interbreed.

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