Logical ReasoningDifficulty: Hard

PT105 S2 Q4 Explanation

An ingredient in marijuana known

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

TopicsWeaken

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Stimulus

An ingredient in marijuana known as THC has been found to inactivate herpes viruses in experiments. In previous experiments researchers found that inactivated herpes viruses can convert healthy cells into cancer cells. use of marijuana can cause cancer.

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
4.

Which one of the following, if true, most seriously weakens

Answer choices

  1. Strengthens0% picked this

    Several teams of scientists performed the various experiments and all of the teams

    By learning that the experiment in the evidence has been corroborated by other experiments, we're making the evidence more trustworthy and thus strengthening the argument.

  2. Correct69% picked this

    The carcinogenic effect of THC could be neutralized by the other ingredients

    Why this is right

    Given that .... THC (which is in marijuana) can do something that has been found to convert healthy cells into cancer cells, How can we argue that ... the use of marijuana cannot cause cancer? We can say, "Using marijuana doesn't cause cancer. Sure, THC by itself could cause cancer by inactivating herpes viruses, but when you use marijuana you don't just ingest THC. The carcinogenic (cancer-causing) effect of THC gets neutralized by the other ingredients in marijuana." We could look at this argument in a sort of Part vs. Whole fashion. Yes, one part of marijuana (THC) causes cancer. But that doesn't mean that ingesting the whole of marijuana causes cancer. After all, other parts of marijuana can neutralize the potential harm of THC.

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

  3. Strengthens, if anything14% picked this

    When THC kills herpes viruses it weakens the immune system, and it might thus diminish the body’s ability to fight other viruses,

    This answer elaborates on the causal mechanism by which THC leads to cancer. If anything, by giving us a better understanding of how THC leads to cancer vulnerability, we're just strengthening this argument. This answer definitely isn't giving us any way to argue that using marijuana doesn't cause cancer.

  4. No Impact: prevent herpes3% picked this

    If chemists modify the structure of THC, THC can be safely incorporated into medications

    We're looking for an answer that will help us rebut the conclusion. We were asking ourselves, How can we argue that ... the use of marijuana cannot cause cancer? This is talking about rearranging THC so that it can prevent herpes. So this isn't giving us any storyline by which someone who uses marijuana would be protected against the cancer-causing potential of THC.

  5. Unrelated to Goal13% picked this

    To lessen the undesirable side effects of chemotherapy, the use of marijuana has been recommended for cancer patients who are

    We need an answer that will help us argue that "the use of marijuana does not cause cancer, despite the fact that THC has been found to do something that can convert healthy cells into cancer cells". This is talking about giving marijuana to people who already have cancer, so it's just irrelevant to our goal.

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