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How can I tell the difference with Strengthen and Necessary Assumption Questions?

Hi everyone,

I understand that in a Strengthen question our task is to identify an AC that will make the conclusion more likely to be true.

In a Necessary Assumption question our task is to identify an AC the argument needs in order to have a chance to be true.

My question is, are there any fundamental differences between the two?

Any input would be highly appreciated. Thank you!


  • qs2159qs2159 Member
    342 karma

    I think they are differed based on their different goals (which you already pointed out)
    Strengthen - correct answer choice makes conclusion more likely to be true
    Necessary - correct answer choice is a must in order for the conclusion to be true (different from sufficient assumption, the conclusion for necessary does not have to be 100% valid, but the answer choice/assumption must be true for the conclusion to be true)

  • andrew.rsnandrew.rsn Alum Member
    831 karma

    A strengthen question will usually have more powerful language in the answer choice, more akin to a sufficient assumption question. Whereas a necessary assumption is weaker in nature - more like a must be true inference question.

    I would definitely checkout the Loophole to learn more about the subtle and not so subtle differences between question types.

  • 422 karma

    You can think about the question stems and what side of the conditional arrow the answer is on which relates to most of the differences I note below.

    Necessary Assumption Question. . .

    Question Stem: Which one of the following is an assumption required by the argument?

    If argument is true, then answer must be true.

    The answer is proven by the argument. This is similar to a MBT question.

    Think of a NA as an unstated assumption. It’s something the author must think/believe in order to reach his conclusion. It’s just not said. The right answer has to be true in order for the argument to work; if you negate it, it weakens the argument. The right answer often addresses an assumption that addresses a big gap in the argument, which makes it easier to paraphrase.

    Correct answer usually includes weak language (looser/less certain), because it makes it easier to accept the statement.

    Weak language cues: some, sometimes, not all, might, can, not always

    They like to include a strengthener as a wrong answer on NA questions because it’s attractive and tempting.; be skeptical of strong language in NA answer choices.

    Strengthen Question. . .

    Question Stem: Which of the following, if true, most strengthens the argument?”

    If answer is true, then argument is strengthened (and we want the one that strengthens the most).

    The answer helps to prove the argument.

    Most often we’re looking for something that strengthens the link between the premises and conclusion; thereby, making it easier to believe the conclusion. Unlike a NA, the answer doesn’t have to be true for the argument to work so you don’t know for sure what to expect in the answer. This makes it harder to prephrase.

    Correct answer usually includes strong language (specific/expresses certainty), because a stronger statement does a better job of strengthening the conclusion.

    Strong language cues: all, always, only, each, every, most, usually, none, never, cannot, must, if/then

  • fin..501fin..501 Member
    edited December 2021 125 karma

    I think the difference between the two is the most stark in that correct Strengthen answers could be false, whereas correct Necessary assumption answers MBT.

    Consider something like this argument "Researchers never find tools in ancient dwellings of People X who lived in area Y 10,000 years ago. Therefore, People X did not use tools." A good strengthen answer could be anything that would even tangentially support the argument...

    Like: "At the time, other groups nearby made tools out of materials that would not naturally degrade over 10,000 years." This would strengthen the argument because it would indicate that, if these people were making tools, researchers would probably have found them, because they would have probably been made from stone or some other material that would stick around for 10,000 years (as opposed to wood or something like that). Therefore, we gain some confidence in the idea that they weren't making tools, even if it's not absolutely conclusive evidence.

    So that is an ex. of a strengthen answer... it's probabilistic, and it could just as easily not be true. If it were not true, maybe we'd want another explanation or info to evaluate the argument, but it could feasibly not be true without making any crazy leaps.

    Consider the negative version "other groups nearby made tools out of materials that would naturally degrade over 10,000 years." This doesn't help the argument anymore, but it doesn't completely destroy it (although I would say it weakens it pretty substantially). The argument is still logically coherent in both cases, Strengthen answers are just increasing the likelihood that the argument is correct - the probability that the explanation is good. If this answer choice was presented for a necessary assumption Q, it would be wrong

    A necessary assumption answer might be "Other nearby groups did not take tools from People X's abandoned dwellings." This is something that absolutely must be true for the argument to hold. Consider the negative version, "other nearby took tools from People X's abandoned dwellings," this makes the argument nonsense. If other groups took tools from People X's abandoned dwellings, then 1. they had tools, and 2. there's a good explanation for why there aren't any tools there now. So this is a necessary assumption because it must be true for the argument to be logically coherent.

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