Logical ReasoningDifficulty: Medium

PT141 S4 Q3 Explanation

Moore: Sunscreen lotions, which

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

TopicsFlaw

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Stimulus

Moore: Sunscreen lotions, which are designed to block skin-cancer-causing ultraviolet radiation, do not do so effectively. Many scientific studies have shown that people who have consistently used these lotions develop, on average, as have rarely, if ever, used them.

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
3.

The reasoning in Moore's argument is most vulnerable to criticism on the grounds

Answer choices

  1. Not Assumed / Too Strong: no other3% picked this

    takes for granted that there are no other possible health benefits of using sunscreen lotions other than

    Since this starts with takes for granted / presumes, we ask ourselves whether this idea qualifies as a Necessary Assumption. It doesn't. It's way too strong and irrelevant. The author doesn't need to assume that there are no possible benefits to using sunscreen; if we say that sunscreen at least has the health benefit of moisturizing one's face, that wouldn't hurt the argument at all. The conclusion is strictly about whether or not sunscreen blocks cancer-causing UV radiation. Anything else it happens to do is out of scope.

  2. Weak Objection17% picked this

    fails to distinguish between the relative number of cases of skin cancer and the severity of those cases in measuring

    This answer is pretty tempting since we might have thought about objecting to the anti-causal conclusion by saying, "Sure, people who use sunscreen have a similar rate of getting skin cancer, but the type of skin cancer is less severe, so therefore the sunscreen is still doing something." This isn't terrible, but the conclusion is saying that sunscreen doesn't effectively block skin-cancer-causing UV radiation. If someone wears sunscreen and gets skin cancer, even a mild case, then isn't it fair to say that their sunscreen did not effectively block skin-cancer-causing UV radiation? If the verb were "does not effectively reduce UV radiation" then we could probably point to a mild case of skin cancer and say, "This is still a sunscreen success story. The skin cancer would have been even worse without the sunscreen." But because of the definitive verb block, if someone wearing sunscreen gets any form of skin cancer, then it's fair to say that the sunscreen didn't effectively block the cancer-causing radiation.

  3. Irrelevant Objection3% picked this

    fails to consider the effectiveness of sunscreen lotions that are not specifically designed to block

    Since this starts with fails to consider / ignores the possibility, we can ask ourselves whether this idea qualifies as a weakening Objection. It doesn't, because this conclusion is strictly about the effectiveness of sunscreens that are designed to effectively block cancer-causing UV radiation. The effectiveness of sunscreens that aren't designed to block that radiation is totally irrelevant to this conversation.

  4. Bad Evidence Match2% picked this

    relies on evidence regarding the probability of people in different groups developing cancer that, in principle, would

    The evidence in this argument isn't about the probability of people in different groups developing cancer (that's a future-looking guess). The evidence is data from scientific studies tabulating the rate at which people did get skin cancer.

  5. Correct75% picked this

    overlooks the possibility that people who consistently use sunscreen lotions spend more time in the sun, on average,

    Why this is right

    Since this starts with fails to consider / ignores the possibility, we can ask ourselves whether this idea qualifies as a weakening Objection. It does, because if the people who use sunscreen spend more time in the sun than people who don't, it's not fair to compare these two groups. The former group is at a much higher risk for skin cancer (since they get more exposure to the sun). If none of them wore any sunscreen, then the people exposed to more sun would have higher rates of skin cancer. The fact that wearing sunscreen brings their cancer rates down to the level of people who have less exposure to the sun shows that the sunscreen is working. On Anti-Causal arguments, we're typically lodging one of two (often related) objections: 1. It would be even worse/better without X 2. These two groups/situations aren't fair to compare Here, we're sort of doing both. These two groups aren't fair to compare because the sunscreen group has a much higher underlying risk of skin cancer due to their greater risk of exposure. Thus, their rate of skin cancer would be even higher if they weren't wearing sunscreen. We can also think of this as offering an Alternate Explanation for the Curious Fact. The Curious Fact was, "How come sunscreen users have the same cancer rate as non-sunscreen users?", and the author's Explanation was, "Because sunscreen doesn't actually help block cancer causing radiation", and here our Alternate Explanation is, "no, the reason they have the same rate is because sunscreen users start out at a much higher risk of skin cancer".

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

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