Logical Reasoning

PT149 · S4 · Q25 The police department has two

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The police department has two suspects for the burglary that occurred last night, Schaeffer and Forster.

Conclusion (so)

Forster must be the burglar.

Evidence

The police department has two suspects: Schaeffer and Forster.

It's not Schaeffer (he has an ironclad alibi).

Evaluate

This argument is attempting to use this reasoning pattern. X is either A or B. X is not A. So, X is B.

That would be a valid argument. The problem is "the police has two suspects: S and F" is not the same as saying "the burglar was either S or F".

This argument is presenting a False Choice. It's acting like S and F are the only two options there are for the burglar, but it never established that they are the only two options.

It only established that the police only have those two as suspects. We don't need to assume that the burglar is definitely one of the suspects the police have.

We could fight this conclusion by saying, .

This author is Assuming a Difference. She's assuming that Forster does not also have an ironclad alibi.

Goal

Let's look for an argument that tries to present two options, rule out one, and conclude the other. But it should be flawed because it never clearly established that those are the only two options we can possibly consider (they will just be the only two things mentioned).

25.

Which one of the following arguments exhibits a flawed pattern of reasoning that is most similar to that exhibited by the argument above?

  1. It has been known for

    Bad Flaw Match

    This is somewhat similar. There are two options presented. But instead of the author assuming, "one of these has to be a YES", this argument is assuming "one of these has to be a NO". The author is illicitly thinking that the two options are mutually exclusive (if one is a YES, the other must be a NO). The original argument was thinking that at least one of the options had to be correct (if one is a NO, then the other must be a YES).

    6% picked this

  2. If Watson, a robbery suspect,

    Topic Trap

    Topic Trap: burglary / robbery Bad Evidence Match As soon as we see the first premise is conditional, we can pretty much bail. It should also smell very fishy that they're using a very similar topic (who's the burglar? who's the robber? who are the suspects?) The flaw here is a Nec vs. Suff error, because the author is thinking if the trigger isn't true, then the outcome isn't true.

    4% picked this

  3. If Iano Industries does not

    Bad Evidence/Conclusion Match

    This one doesn't really have any matching features. It has a conditional premise, which immediately should cause us to bail. The conclusion is a "should" claim, which could immediately cause us to bail.

    2% picked this

  4. Correct

    Baxim Corporation announced last year

    Why this is right

    This replicates the False Choice of the original. The author is thinking that "one of these two options is definitely the one", even though there was never any language cinching in that idea. This author, like our original argument, is assuming "If one of them is a NO, then the other must be a YES". But just like the original argument, this is vulnerable to the objection of "isn't it possible that both of them are NO's, and we just need to expand our list of contenders?" Our original author thought the burglar must be S or F, but all we knew is that S and F were two suspects under consideration. This author thinks that Baxim will move to E or R, but all we know is that E and R are two sites under consideration.

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

    76% picked this

  5. The only viable candidates in

    Pretty Valid Bad Evidence Match

    This argument can't replicate our False Choice flaw because in this argument the author does establish that the two options being discussed are the only two options we are allowed to consider: the only viable candidates are S and G If we were objecting to this argument, we'd pretty much be stuck arguing that "political analysts don't know what they're talking about", and that's not similar to the original argument.

    12% picked this

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