Logical Reasoning

PT141 · S4 · Q3 Moore: Sunscreen lotions, which

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Moore: Sunscreen lotions, which are designed to block skin-cancer-causing ultraviolet radiation, do not do so effectively.

Conclusion

Sunscreen lotions do not effectively block skin-cancer-causing UV radiation.

Evidence

Many studies show that people who have consistently used these lotions develop, on average, as many skin cancers as those who have rarely, if ever, used them.

Evaluate

This is an Anti-Causal argument, because the conclusion is saying "X does not cause Y". The evidence is that people who use sunscreen tend to get as much skin cancer as do people who don't. The classic Anti-Causal objection is to say, .

Consider this Anti-Causal analogy: Contact lenses, which are designed to improve people's vision, do not do so effectively. Studies show that people who wear contact lenses are able, on average, to see as far down the road as are people who don't wear contact lenses.

We would shout,

Similarly, maybe the people who wear sunscreen are people who really need it (they are super fair-skinned or they spend tons of time out in the open sun) whereas people who don't wear it are darker-skinned, indoor types.

If the first group weren't wearing sunscreen, then their skin cancer levels would be through the roof. The fact that wearing sunscreen brings their skin cancer numbers down to the same level as those of darker-skinned, indoor types makes it seem like the sunscreen is effectively blocking some cancer-causing radiation.

Goal

We need to defend the idea that sunscreen DOES help block our cancerous UV radiation, so we need to "make an excuse" for the evidence. We need a way to explain why sunscreen users have similar skin cancer rates to non-sunscreen people, such that we can still argue that the sunscreen IS helping the sunscreen users to block out cancerous UV rays.

3.

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

  1. takes for granted that there

    Not Assumed / Too Strong: no other

    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% picked this

  2. fails to distinguish between the

    Weak Objection

    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.

    17% picked this

  3. fails to consider the effectiveness

    Irrelevant Objection

    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.

    2% picked this

  4. relies on evidence regarding the

    Bad Evidence Match

    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.

    2% picked this

  5. Correct

    overlooks the possibility that people

    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.

    76% picked this

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