Logical ReasoningDifficulty: Hard

PT23 S2 Q8 Explanation

The caterpillar of the monarch

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

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Stimulus

The caterpillar of the monarch butterfly feeds on milkweed plants, whose toxins make the adult monarch poisonous to many predators. The viceroy butterfly, whose caterpillars do not feed on milkweed plants, is very similar in appearance to the monarch. Therefore, it can be concluded because of its visual resemblance to the monarch.

What this question is testing

Weaken

Your task

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

Common trap

Answers that look negative but attack a claim the argument never relied on.

Winning move

Find the assumption the argument depends on, then pick the choice that undermines 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
8.

Which one of the following, if it were discovered to be true, would most seriously

Answer choices

  1. Trap10% picked this

    Some predators do not have a toxic reaction to insects that feed

    Already Acknowledged by Author Too Weak: some The paragraph only said that monarchs were poisonous to "many" predators, so he's allowed for the possibility that monarchs (and other milkweed eaters) aren't poisonous to all predators. Since some only means "there is at least one predator that doesn't have a toxic reaction to milkweed insects", it's unlikely to be a correct answer on question types like Strengthen / Weaken / Paradox, where we want the most impactful answer.

  2. No Impact13% picked this

    Being toxic to predators will not protect individual butterflies unless most members of the species to which such

    The author is thinking that viceroys are not poisonous. Any of them. Meanwhile, he thinks that monarchs are poisonous (presumably most / all of them). The author thinks that what is protecting individual viceroy butterflies is the fact that they look like a different species, in which most members are toxic to predators. In order for this answer to apply to what we know of viceroys, we'd have to rewrite it like Being very visually similar to a species whose members are toxic to many predators will not protect butterflies unless .... That would at least be referring to viceroys, and then it could say something that would undermine the author's hypothesis about visual resemblance to monarchs being the viceroy's shield against predators.

  3. Strengthens10% picked this

    Some of the predators of the monarch butterfly also prey

    This affirms something the author is assuming. If none of the viceroy's predators matched the monarch's predators, that would hurt the author's hypothesis. He thinks that predators are scared from viceroys because they think, "Oh, it's one of them nasty monarchs I've tried eating before".

  4. Correct64% picked this

    The viceroy butterfly is toxic to

    Why this is right

    This provides an Alternate Explanation for why viceroys are seldom preyed on. It almost melts your brain to process it, because the author builds up this story like, Monarchs eat milkweed, so they're poisonous. Viceroys don't eat milkweed, (so they're not poisonous?) But they're seldom preyed on, so it must be because they look like monarchs. This answer is saying, "No, it's because they're also poisonous. You were just assuming they weren't because they don't eat milkweed, but there's more than one way to be poisonous!"

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

  5. Strengthens, if anything3% picked this

    Toxicity to predators is the principal means of protection for only a

    This answer is saying it's actually pretty rare for a butterfly species to protect itself via being toxic to predators. This makes us more inclined to believe that the viceroy is seldom preyed on, not because it's toxic to predators, but because it looks very similar to one of those rare butterfly species (the monarch) that is toxic to predators.

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