Logical Reasoning

PT107 · S1 · Q7 In Debbie’s magic act, a volunteer

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In Debbie’s magic act, a volunteer supposedly selects a card in a random fashion, looks at it without showing it to her, and replaces it in the deck.

Conclusion (concluded)

Debbie uses neither sleight of hand, nor a trick deck, nor a planted volunteer to achieve her effect.

Evidence

The skeptic was trying to figure out how Debbie achieve the 'magic' effect of cutting the deck to reveal the audience member's secret card.

In trial 1, she was videotaped and no sleight of hand was found.

In trial 2, the skeptic provided the deck of cards.

In trial 3, the skeptic was the audience member who selected the card.

Each time, Debbie was still able to achieve her effect.

Evaluate

Given ... what the skeptic was able to discover with those three trials, How could we argue that ... Debbie did use sleight of hand, or a trick deck, or a planted volunteer?

In trial 1, it was videotaped. But could there still have been sleight of hand? Sure, maybe. Maybe the angle of the camera was unable to detect the sleight of hand.

In trial 2, the skeptic provided the deck. But could it still have been a trick deck? Sure, theoretically, the skeptic could have provided Debbie with a trick deck, but that's nonsensical. The skeptic isn't trying to help Debbie succeed in doing the trick. He's trying to figure out how to thwart her.

In trial 3, the skeptic was the audience member who picked the card. But could Debbie still have used a planted volunteer to do the trick? No, that's like what we said with trial 2. That would mean that the skeptic was the planted volunteer. That's nonsensical, too.

So are we really just arguing that Debbie does use sleight of hand, and it's just that the videotape didn't catch it?

Yes, possibly. Otherwise, we're framing the tension like this: Given that ... trial 1 had no sleight of hand, trial 2 had no trick deck, and trial 3 had no planted volunteer, How could we argue that ... Debbie does use sleight of hand, a trick deck, or a planted volunteer?

Goal

For many of us, we're going to feel pretty stumped by this argument and head to the answers thinking, "let me find an answer that allows me to accept the evidence but still argue that Debbie was using sleight of hand, trick, deck, or planted volunteer.

7.

Which one of the following most accurately describes a flaw in the skeptic's reasoning?

  1. Correct

    The skeptic failed to consider

    Why this is right

    When an answer begins with fails to consider / ignores the possibility, we can assess the idea that follows like we're doing Weaken. Could we object to this argument by saying that, "Debbie doesn't always use the same method to achieve her effect"? Yes. We could say, "Sure, Trial 1 showed no sleight of hand. That's because Debbie was using a trick deck to achieve the effect, since she knew you were videotaping her." And then the skeptic would say, "B-but, in trial 2, I supplied the deck, which obviously was not a trick deck." But since Debbie can achieve her effect more than one way, we can say, "Yes, during Trial 2 she used sleight of hand, since she knew she had to use your deck." And then for trial 3, we can say she used a trick deck or sleight of hand, rather than a planted volunteer. If Debbie has the flexibility to use sleight of hand or a trick deck or a planted volunteer, then she could have kept switching her method to elude the mode of detection the skeptic was using. For the skeptic to have really proven this conclusion, he would have needed to combine all his methods into one trial. "Debbie, we're videotaping you. I'm supplying the deck, and I'm going to be the audience member who picks the card." That would exclude all three methods simultaneously, which would allow the skeptic to derive his conclusion.

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

    67% picked this

  2. The skeptic failed to consider

    Not an Objection

    Since this begins with fails to consider / ignores the possibility, we can ask ourselves whether it weakens to say, "Hey, author -- you can detect sleight of hand other ways than videotaping"? No, that doesn't weaken. As long as videotaping is a way to detect sleight of hand, then trial 1 showed that (at least during trial 1) Debbie wasn't using sleight of hand.

    4% picked this

  3. The skeptic failed to consider

    Didn't Fail to Consider

    Since this begins with fails to consider / ignores the possibility, we can ask ourselves whether it weakens to say, "Hey, author -- Debbie's trick requires both sleight of hand and a trick deck"? Yes, that would weaken, because it would basically contradict the conclusion. However, it's not true to say that the skeptic failed to consider this possibility. After all, the skeptic devised trials to figure out whether sleight of hand or trick decks were involved. The skeptic can say, "I absolutely considered whether Debbie uses both. But ... I ruled out sleight of hand via trial 1 and ruled out trick deck via trial 2. So, I know that Debbie isn't using either of those methods, let alone both of them." For any Flaw answer to be correct, we have to be able to answer "yes" to both of these questions: 1. Is this answer descriptively accurate? 2. Does this answer make a good complaint about the logic? 99% of the time when we see fails to consider / ignores possibility, #1 is true, and so we're really just asking ourselves about #2 (would this be a good complaint about the logic). But occasionally we'll be getting rid of these answers because #1 is false, the author didn't fail to consider X. The author is trying to prove X is false.

    4% picked this

  4. The skeptic failed to consider

    Not an Objection

    Since this begins with fails to consider / ignores the possibility, we can ask ourselves whether it weakens to say, "Hey, author -- maybe Debbie uses some method besides those three you mentioned"? No, that doesn't weaken. That totally agrees with the author. He thinks she uses none of those 3 listed methods; so he believes that she uses some other method.

    23% picked this

  5. The skeptic failed to consider

    Not an Objection

    Since this begins with fails to consider / ignores the possibility, we can ask ourselves whether it weakens to say, "Hey, author -- her success is not just a coincidence." No, that doesn't weaken. The skeptic doesn't think that Debbie's ability to pull off this effect each time is a coincidence. He understands she's doing a magic trick. He's trying to figure out her method and thinks he has ruled out three possibilities.

    2% picked this

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