Logical ReasoningDifficulty: Medium

PT149 S3 Q18 Explanation

Herbalist: Many herbal medicines work

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

TopicsNecessary Assumption

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Stimulus

Herbalist: Many herbal medicines work best when they have a chance to influence the body gently over several months. However, many of these herbal medicines have toxic side effects when taken daily for such long periods. Therefore, at least some people who use herbal medicines daily should or two, to give the body a chance to recuperate.

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
18.

Which one of the following is an assumption required by the

Answer choices

  1. Correct76% picked this

    At least some people who use herbal medicines daily use them for periods long enough for the medicines

    Why this is right

    This was not an answer I saw coming, but because it's so weakly worded (at least some), it's tempting. When we negate weak wording we get a strong idea: No one who uses herbal meds daily uses them for long enough to have side effects. Does that weaken the argument? Heck yeah! If no one uses them long enough to have the toxic side effects, then there's not even a Problem that needs solving, so the author's advice to "skip a dose for a day or two" is completely pointless. On Necessary Assumption, if negating an answer choice turns that answer into a big objection, then it's the correct answer.

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

  2. Weakens3% picked this

    At least some herbal medicines work less well in achieving their desired effects if one occasionally skips one’s usual dose

    There's no reason we can say the author needs to believe this, when this idea actually presents a downside to following her advice. According to this, if you follow the author's advice, you'll be making your herbal meds work less well. We don't know one way or the other what the author would say about this issue, but it's more conservative to think she's hoping that by only skipping a dose for a day or two, you're still getting the same benefit, just without the toxic side effect harm.

  3. Weakens2% picked this

    Some herbal medicines have toxic side effects when taken for several months, even if the usual dose is occasionally skipped for a day or

    There's no reason we can say the author needs to believe this, when this idea actually makes it seem like her recommendation wouldn't succeed, for some herbal meds. According to this, if you follow the author's advice, you might not be spared the toxic side effects, because for some herbal meds, you get those side effects even if you follow the author's advice of sporadically skipping a dose.

  4. Unrelated to Goal Too Strong: anyone3% picked this

    Anyone who uses herbal medicines should give those medicines a chance to influence the body gently over

    This answer has nothing to do with the author's conclusion, which is about skipping doses intermittently, if you're already taking herbal meds daily. This answer makes a very bold claim "every single person who uses herbal meds should give them a chance to influence the body over at least several months". The first sentence, which was not part of the argument, is where people would find some support for this notion. But just because the author said, "many herbal meds work best when absorbed gently over several months", that doesn't mean she holds the position that "every single person who uses any herbal med should use it for several months".

  5. Reversed Logic16% picked this

    One should occasionally skip one’s usual dose of an herbal medicine for a day or two only if doing so will reduce or eliminate

    "Only if" is a necessary indicator meaning that any idea that follows "only if" should go on the right of the arrow. So this answer looks like this Should occasionally skip ? reduce / eliminate usual dose for a day or two toxic side effects But this doesn't match the move from Premise to Conclusion. It's reversed. The author was arguing Since ... Therefore ... long term use comes should occasionally with toxic side effects skip a dose for a we'd want to reduce day or two or eliminate

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