Logical ReasoningDifficulty: Hard

PT127 S3 Q25 Explanation

Chef: This mussel recipe's

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

TopicsNecessary Assumption

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Stimulus

Chef: This mussel recipe's first step is to sprinkle the live mussels with cornmeal. The cornmeal is used to clean them out: they take the cornmeal in and eject the sand that they contain. But I can skip this step, because farm raised and therefore do not contain sand.

What this question is testing

Necessary Assumption

Your task

Find the assumption the argument requires in order for its conclusion to hold.

Common trap

Answers that would help the argument but aren't strictly required (sufficient, not necessary).

Winning move

Negate each choice — the right one breaks the argument when negated.

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

The question
25.

Which one of the following is an assumption required by the

Answer choices

  1. Irrelevant Quality6% picked this

    Cornmeal is not used to clean out farm-raised mussels before they

    This has the lovable defender-style "not", so we should pause and perform the negation test. Does it weaken the argument if we say, "cornmeal IS used to clean sand out of farm-raised mussels before they reach seafood markets"? Nope. That would actually align with the author's intermediate conclusion that farm-raised mussels are free of sand. It certainly doesn't give us any way to argue that the chef DOES still need to perform the first step of sprinkling his mussels with cornmeal. If anything, it seems to do the opposite of that.

  2. Out of Scope (other than sand)22% picked this

    Mussels contain no contaminants other than

    If we negate this and say "mussels DO contain other contaminants besides sand", that might feel like it gives us a way to say, "See, author? So you DO still need to do the first step of sprinkling your mussels with cornmeal." But ... does sprinkling mussels with cornmeal get rid of other contaminants? We have no idea. So that would be a pretty weak objection (unclear impact). The only contaminant the argument seemed concerned with was sand, so "other than sand" feels out of scope.

  3. Irrelevant Quality7% picked this

    Sprinkling the mussels with cornmeal does not affect

    This has the lovable defender-style "not", so we should pause and perform the negation test. Does it weaken the argument if we say, "hey, author, sprinkling the mussels with cornmeal DOES affect their taste"? Yeah, it might! I mean, maybe that's why the chef should still sprinkle cornmeal on the mussels. Even though he doesn't need the cornmeal to eject sand (since they don't have sand), he still needs it for the eventual taste? Ultimately, this negation isn't as strong an objection as that of the correct answer, because "affects their taste" has unclear impact. If the answer were phrased more like "sprinkling the mussels with cornmeal is not critical to get the desired taste from this recipe", then this would be a great answer.

  4. Irrelevant Relationship2% picked this

    The chef's mussel recipe was written before farm-raised mussels

    The timeline of when the recipe was written is totally irrelevant to whether the chef does / doesn't need to perform the first step. If we negate this and say, "the recipe was written after farm-raised mussels were already available", that doesn't weaken the argument. The recipe might just be assuming that most people don't have access to farm-raised mussels and so it contains a step for removing sand.

  5. Correct62% picked this

    The mussels the chef is using for the mussel recipe came from

    Why this is right

    If we negate this, then the entirety of the author's evidence is completely irrelevant to the conclusion. The conclusion is about whether this chef can skip the cornmeal step when following this mussel recipe. The evidence is about mussels from seafood markets. If the chef is not using mussels from seafood markets, then the premises are totally irrelevant to the chef's situation. The chef may very well have sandy mussels that need a cornmeal bath. We call this style of correct answer Assumes Applicability, because it has this dumb feeling of "remember all the general stuff I talked about in the premises? We're assuming that stuff applies to the specific thing we're talking about in the conclusion".

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

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