Logical Reasoning

PT148 · S4 · Q16 Last year, a software company

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Last year, a software company held a contest to generate ideas for their new logo.

Conclusion (so)

Juan must have entered the contest.

Evidence

Juan has a T-shirt with the new logo.

Everyone who entered the contest would receive a T-shirt with the new logo.

Evaluate

Just because Juan has a T-shirt that was given away in this contest, does that prove that Juan entered the contest? No, he might have gotten the T-shirt some other way. Maybe he works at the company and had access to the shirt before the contest even started. Maybe his friend Tara entered the contest and when she got her free shirt she gave it to Juan.

Whenever we're doing a Flaw question and see conditional logic indicator words (i.e. if, when, any, all, every, each, no, ,only if, only, must, ensures, unless, etc), we should suspect that we're about to see the #1 Famous Flaw: Necessary vs. Sufficient.

The word "everyone" is a universal, so it's a Sufficient (left side) indicator.

entered the contest → received new logo shirt

Once an author has provided a conditional relationship in her premises, we look to see if she uses it illegally backwards or in opposite fashion, e.g.

X has the new shirt. X didn't enter contest. So X entered contest. So, X doesn't have shirt

Both of these are technically the same flaw. Whether the author illegally negated or reversed the conditional relationship, we can call him out on confusing his Necessary and Sufficient conditions.

Goal

Look for an answer calling out the Necessary vs. Sufficient flaw or just calling out the fact that there are other possible ways to get that T-shirt.

16.

The reasoning in the argument is flawed in that the argument

  1. infers a causal relationship when

    Wrong Flaw: not Causal

    There wasn't any correlation presented in the evidence, just a rule about all contest entrants getting a T-shirt. The author is assuming / inferring that entering the contest is what caused Juan to get the T-shirt. We would be fine calling out this and saying that the author is failing to consider alternative explanations for how Juan could have gotten the T-shirt. But if the Cause / Effect relationship being inferred is CAUSE: Juan entered contest EFFECT: Juan got T-shirt then this answer is saying, "The evidence only supports a correlation between Juan entering the contest and Juan getting a T-shirt", but that's not accurate. A correlation is a before/after relationship, a concurrent relationship, or a statistical relationship. Maybe if we really, really wanted to stretch definitions, we could try to make this answer work, but it wouldn't be the "best available" answer, since there is an answer choice naming the conditional logic flaw the argument is making, which is how the argument is most vulnerable to criticism.

    7% picked this

  2. Correct

    takes a condition that is

    Why this is right

    "Entering the contest" is sufficient for the particular outcome of "getting the new T-shirt": Everyone who enters would receive the new T-shirt. Enter contest ? T-Shirt The author's reasoning is that, "If Juan has T-shirt, then Juan entered contest". T-shirt ? Enter contest In her reasoning, "enter contest" is on the right side, the necessary condition. More conversationally, we're saying, "Yes, entering the contest is one possible / sufficient way to get a T-shirt. But that's not the only way to get a T-shirt. No one said you had to enter the contest to get one. Maybe people who buy software from the company get a T-shirt. Maybe Juan attended an office party with his husband (who works there), someone spilled wine on Juan's shirt, and they gave him a T-shirt to change into"

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

    86% picked this

  3. infers that every member of

    Wrong Flaw: not Part vs. Whole

    Is the author's conclusion saying "every member of a group has a feature in common"? Nope, it's saying "Juan entered the contest". There's no Part to Whole move happening here.

    3% picked this

  4. has a premise that presupposes

    Wrong Flaw: not Circular

    Is the author's evidence a restatement of her conclusion? Nope, it's just saying "Juan entered the contest". There was no premise that said / assumed that Juan entered the contest, just the conclusion.

    2% picked this

  5. constructs a generalization on the

    Wrong Flaw: not Sampling

    Is the author's conclusion a generalization? Nope, it's saying "Juan entered the contest". And this conclusion was based on a conditional rule (everyone who enters gets a shirt) plus a fact that Juan has a shirt.

    2% picked this

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