Logical ReasoningDifficulty: Hard

PT149 S1 Q21 Explanation

Archaeologist: Our team discovered

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

TopicsNecessary Assumption

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Stimulus

Archaeologist: Our team discovered 5,000-year-old copper tools near a Canadian river, in a spot that offered easy access to the raw materials for birchbark canoes—birch, cedar, and spruce trees. The tools are of a sort used by the region’s Aboriginal people in making birchbark canoes in more people in Canada built birchbark canoes 5,000 years ago.

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
21.

The archaeologist’s argument depends on the assumption that the copper tools that

Answer choices

  1. Too Strong: no value1% picked this

    had no trade value 5,000 years

    Why does the author have to assume these rad copper tools had zero trade value. If they had some trade value, would that be an objection? No.

  2. Correct55% picked this

    were present in the region 5,000

    Why this is right

    If we negated this and said, "Hey author, these tools weren't even in this region 5,000 years ago", then that would badly weaken his case that these tools show that the Aboriginal people were making birchbark canoes 5,000 years ago. In most LSAT arguments involving some found piece of archeological evidence, some artifact, the author tries to learn something about the local inhabitants from this found object. Those authors are always assuming that the found object is actually a local object, not some object that was brought from a different region and just dropped there.

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

  3. Too Strong: only4% picked this

    were designed to be used on material from birch, cedar, and

    The author only needs to assume that these tools were relevant / useful to making birchbark canoes. She doesn't need to assume that the tools only had that use. Just because birch, cedar, and spruce were the only trees mentioned in relation to raw materials for building birchbark canoes, that doesn't mean the tools were only good for those trees. This is a common trap answer: Only Ones Mentioned → The Only Ones

  4. Too Strong: only12% picked this

    were the only kind of tool that would have been used for canoe making

    The author needs to assume that these copper tools could have been used to make canoes 5,000 years ago, and she's concluding that they were used. But these doesn't need to believe that no other tools were ever used in the canoe building process. If I found evidence that a certain civilization had spatulas, maple syrup, and flour, I can speculatively conclude that "This civilization knew how to make pancakes!" without committing myself to believing that all you need to make pancakes is a spatula, maple syrup, and flour.

  5. Out of Scope27% picked this

    are not known to have been used by the region’s Aboriginal people for any task

    Out of Scope: other than canoe making This is yet another Only Thing Mentioned → The Only Thing trap answer. Most of the trap answers on this problem are using this same trap, and making answers that are too extreme. The author thinks that these tools were used at some point to gather some raw materials from some local trees and turn them into a birchbark canoe. (C) they only gathered raw materials from those 3 trees mentioned. (D) they were the only tools used to make the canoe. (E) they were used to make only canoes.

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