Logical Reasoning

PT105 · S2 · Q21 Some people have been promoting

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Some people have been promoting a new herbal mixture as a remedy for the common cold.

Sufferer's Conclusion

The herbal mixture is obviously not effective.

Sufferer's Evidence

Suppose it were effective -- in that world, almost everybody with a cold would be using it, since most people with colds wish to recover quickly.

But there are many people who have colds but do not use the mixture.

Evaluate

There are some serious logic problems with this argument, but who cares, it's a Method question. We're just supposed to describe it accurately.

The signature move the author made here was arguing via a contrapositive (of a counterfactual).

If you were right, then X would be true. But X isn't true. Thus you're not right.

Goal

Let's look for something that feels like it captures this contrapositive of a counterfactual.

21.

Which one of the following most accurately describes the method of reasoning the cold sufferer uses to reach the conclusion of the argument?

  1. Correct

    finding a claim to be

    Why this is right

    "Doing X on the grounds that Y" means that X is the conclusion and Y is the evidence. Does the conclusion find a claim to be false? Sure, it finds the claim [this herbal remedy is effective] to be false, because it concludes the mixture is not effective. Is the evidence saying that this claim, if true, would have consequences that are false? Yes, the evidence says that if it were true that the mix were an effective cold remedy then a consequence would be almost everybody with a cold would be using it but that consequence is false many people w/ colds do not use the mixture

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

    62% picked this

  2. accepting a claim on the

    Bad Conclusion/Evidence Match

    "Doing X on the basis of Y" means that X is the conclusion and Y is the evidence. Did the conclusion accept a claim? Nope, it rejected a claim, the claim that "this herbal mix is effective". If we wanted to play along with this answer, we could say that the author's conclusion is accepting the claim "this mixture is not effective". In that case, the evidence would have to be public opinion on whether "this mixture is not effective". But the evidence is not saying, "people don't think this mix is effective". The author isn't citing their opinion; he's only citing their behavior (whether many people do or don't currently use this remedy).

    7% picked this

  3. showing that conditions necessary to

    Opposite: are met

    The author is showing that conditions (almost everyone is using the remedy) which are necessary to establish the truth of a claim (this remedy is effective) are not being met. In saying, "Suppose the mix would effective, it follows that almost everybody would be using it" would be diagrammed like this: mixture effective → almost everyone using it (claim) (necessary condition)

    13% picked this

  4. basing a generalization on a

    Bad Conclusion / Evidence Match

    "Basing X on Y" means that X is the conclusion and Y is the evidence. Was the conclusion a generalization? Nope, it was a specific claim about this cold remedy: "It is obviously not effective" Is the evidence a representative group of instances? No, it's a hypothetical, followed by a hypothetical consequence, followed by an observation about the world in which we live in. There's no "representative sample" appealed to.

    15% picked this

  5. showing that a measure claimed

    Bad Conclusion Match

    The thing the author is showing in an argument is her conclusion. Was this conclusion saying that the cold remedy not only is ineffective at getting rid of your cold, it actually makes it harder to get rid of your cold? No, the conclusion only says the remedy is ineffective, not that it makes the situation worse.

    2% picked this

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