Logical Reasoning

PT120 · S3 · Q14 Overexposure to certain wavelengths of

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Overexposure to certain wavelengths of strong sunlight is the main cause of melanoma, a virulent form of skin cancer.

Recommendation

Everyone should put adequate sunblock on skin exposed to strong sunlight.

Evidence

Overexposure to certain wavelengths of strong sun is the main cause of melanoma (bad skin cancer).

Adequate sunblock = any preparation that prevents sunburn over a prolonged period of exposure.

Evaluate

This argument seems to have a big missing link as it tries to connect "adequate sunblock" to the concern about skin cancer:

adequate → prevents — ? → prevents sunblock sunburn overexposure to melanoma wavelengths?

Goal

Look for something suggesting that adequate sunblock may prevent sunburn, but won't help protect against melanoma, or look for something bringing up a potential bad thing about putting adequate sunblock on exposed skin (maybe it has some chemical in it that's bad for us).

14.

Which one of the following, if true, most weakens the recommendation that people wear adequate sunblock?

  1. Correct

    There is no evidence that

    Why this is right

    This hurts the argument because the recommendation was definitively connected to melanoma. The argument said, "For this reason, doctors urge we put on adequate sunblock." All we're told about adequate sunblock is that it prevents sunburn. But according to this answer, preventing sunburn has nothing to do with preventing melanoma (it's different wavelengths of sunlight). So this answer weakens the argument by making the premise in the final sentence be irrelevant to the Goal of the Recommendation. The doctors are recommending adequate sunblock as a means of avoiding melanoma, and they've defined adequate sunblock as "anything that prevents sunburn", but that means that there could be a sunscreen that just blocks sunburn wavelengths (so it would qualify as adequate sunblock) but doesn't block melanoma wavelengths (since they are entirely distinct).

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

    61% picked this

  2. There are people who have

    Weaker Than Correct Answer

    This weakens somewhat, because it points out a potential disadvantage of recommending sunblock to everyone (some people will likely have allergic reactions). This isn't a huge weakener, since people would obviously rather risk an allergic reaction, until they find a sunblock that works for them, than to risk getting melanoma. And so the impact of this answer is not nearly as strong as the correct answer, which made the argument's premise seem downright irrelevant to the conclusion.

    8% picked this

  3. Many sunblocks need repeated applications

    No Impact

    This isn't really an objection. It's not posing much of a hurdle to this plan's success. It's just saying that many sunblock's would need to be periodically re-applied, if you're going to be out in the sun for a long time. Okay, so re-apply the sunblock. That's no big objection. The doctors defined adequate sunblock with a weird noun, "any preparation that prevents sunburn". That noun seems to be kind of like "any regimen / protocol", which could certainly include the idea of needing to periodically re-apply another 'dose' of sunblock.

    9% picked this

  4. Toxins contained in certain chemical

    Too Vague

    There's a nonzero chance that the chemical compounds this answer is talking about are in sunblock, in which case this answer would be suggesting that sunblock itself could lead to melanoma. But this answer just says "certain chemical compounds". There are potentially millions of those. We don't know whether this answer is saying anything about any ingredient in sunblock. We could consider this whisper of doubt/concern if all the other answers did nothing or went the wrong way, but we have better options.

    9% picked this

  5. Sunburns appear immediately after exposure

    Unclear Impact

    This does seem to point a potentially meaningful distinction between sunburn and melanoma, but it's not clear how this distinction relates to the recommendation to put on adequate sunblock. Since sunburns apparently show up earlier than melanoma, then preventing sunburns could still potentially prevent melanoma (if the two are connected). This answer isn't really giving us any reason to think that sunburns and melanoma are or aren't connected.

    13% picked this

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