Logical Reasoning

PT124 · S2 · Q20 On some hot days the

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On some hot days the smog in Hillview reaches unsafe levels, and on some hot days the wind blows into Hillview from the east.

Conclusion (Therefore)

There are some days in Hillview when the wind blows from the east and the smog reaches unsafe levels.

Evidence

On some hot days in Hillview, the wind blows from the east. On some hot days in Hillview, the smog reaches unsafe levels.

Evaluate

Because both premises and the conclusion are quantified Some claims, we might want to think about Trait Overlap inferences:

Some A's are B Most A's are B All A's are C Most A's are C infer: Some B are C Some B are C

There aren't any trait overlap inferences where you combine two Some facts about the same group.

I can say "Some men are U.S. Senators" and "Some men live in Mongolia", and that doesn't allow us to infer that Some U.S. Senators live in Mongolia.

Some is a very weak quantifier that means "at least one".

There was at least one hot day where the wind blew from the east. There was at least one hot day where the smog reached unsafe levels.

Does there have to be a day when both things occurred?

No, maybe eastern wind happened on Monday and unsafe smog happened on Thursday.

Goal

Look for an answer saying we can't prove an overlap between "unsafe smog" and "eastern wind", since it's entirely possible that those two things happened on different hot days.

20.

The reasoning in the argument is flawed in that the argument

  1. mistakes a condition that sometimes

    Not Necessary vs. Sufficient

    This sounds like the #1 famous flaw Necessary vs. Sufficient, in which the author presents a conditional rule in the evidence, and then illegally uses that rule (by reversing it or negating it) in tandem with some other fact to derive the conclusion. There were no conditional claims anywhere in this argument, so there's no chance the author was thinking about anything that "necessarily accompanies unsafe levels of smog". We were told that the condition of "hot days" sometimes accompanies unsafe levels of smog. For the rest of this answer to be true, the argument would have had to argue, "On Day X, there was unsafe smog. Thus, on Day X it must have been hot" or argue "On Day X, it wasn't hot. So therefore on Day X there wasn't unsafe smog."

    25% picked this

  2. Correct

    fails to recognize that one

    Why this is right

    This is a historically funny-hard answer. It's normal to think, "Wha?" on a first pass, but it's 170 behavior to defer on a confusing answer rather than eliminating it just because we don't understand it. Given that our complaint with the argument was something like, "Heyyyy --- you can't prove an overlap between east wind and unsafe smog!", it should somewhat please us to see that this answer is talking about whether or not two sets overlap. What it's saying is that we can have one set, which is the set of "Hot Days in Hillview": {July 15, 19, 22, 30, Aug 1, 3, 9, 14, 20, 25} It has some member in common with two other sets. Here's the set of "Eastern wind days in Hillview": {July 19, 20, 21, Aug 3, 4, 20, 21} Here's the set of "Unsafe Smog days in Hillview": {July 4, 15, Aug 9, 10} We can see that some hot days had unsafe smog: July 15 and Aug 9 Some hot days had wind from the east: July 19, Aug 3, and Aug 20 But there are no dates in common between the set of "unsafe smog" days and the set of "eastern wind" days. In other words, they don't have to overlap.

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

    55% picked this

  3. uses the key term “unsafe”

    Not Equivocation

    This describes one of the ten famous flaws, Equivocation, in which the author uses the same term or concept twice but to mean two very different things. That didn't happen here. "Unsafe" meant the same thing every time it was used. Equivocation is almost never the correct answer.

    0% picked this

  4. contains a premise that is

    Not Circular

    This describes one of the ten famous flaws, Circular Reasoning, in which the author's evidence restates the conclusion or presumes the truth of the conclusion. The conclusion was that on some days with eastern wind there is unsafe smog. There definitely was no premise that repeated that. Did either of the two premises presume that? In order to say, "on some hot days the smog is unsafe", do you need to assume that "some days with eastern wind have unsafe smog"? Of course not. Nor do you need to presume the conclusion in order to say the other premise. Answers that describe Circular Reasoning are almost always wrong: - conclusion restates the premise - assumes what it sets out to prove - presumes the truth of the conclusion - presupposes what it seeks to establish

    1% picked this

  5. infers a particular causal relation

    Not Causal

    This describes one of the ten famous flaws, Causal Overconfidence, in which the author overconfidently concludes one potential causal explanation for a curious fact when other possible explanations still exist. Any Flaw answer phrased like infers X from Y means that X should match the conclusion and Y should match the evidence. Is the conclusion talking about "a particular causal relation"? No. There's no causal verb in the conclusion. I can say, "On some days when I go to church, I want NFL football." That does not imply that going to church caused me to watch football.

    18% picked this

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