#25 - The police department has two suspects for the

[Administrator]

Complete Question Explanation

Parallel Reasoning—Flaw. The correct answer choice is (D)

Here, the author reaches a flawed conclusion about who committed a burglary. The police suspect
that either Schaeffer or Forster committed the burglary. Since Schaeffer has an ironclad alibi, the
author concludes that Forster must be the burglar.

This is an example of a False Dilemma. Just because the police have identified two suspects does
not necessarily mean that either suspect is in fact the burglar. The burglar may be some other person
entirely. This is a Parallel Reasoning—Flaw question. Our prephrase is that the correct answer
choice will contain an argument in which the author uses a False Dilemma to reach the conclusion.

Answer choice (A): Unlike in the stimulus, this argument does not establish that the two options
were either building a new primate house or refurbishing its polar bear exhibit. While the conclusion
is flawed because no evidence has been offered to explain why they will not refurbish the polar bear
exhibit, this is not a False Dilemma because the argument has not established an either/or situation.

Answer choice (B): Here, the argument is valid, resulting from the application of a conditional rule
to a fact.

Answer choice (C): In this case, the author weighs two options and decides which course of action
the company should take, which is entirely dissimilar to the argument’s use of a False Dilemma.

Answer choice (D): This is the correct answer choice, because it displays a False Dilemma. Just
like in the stimulus, although the argument does not explicitly create an either or relationship, the
fact remains that the company can have just one headquarters. However, the evidence does not
establish that Evansville and Rivertown are the only possibilities. So, evidence that the company will
not move its headquarters to Evansville does not definitively prove that it will move to Rivertown.

Answer choice (E): Here, the answer choice begins promisingly, telling us that the only viable
candidates are Slater and Gonzalez. However, the conclusion does not result from a False Dilemma
because the conclusion is probabilistic rather than definitive. In order to be a False Dilemma, the
conclusion must be definitive.

[candaceross]

Hello,

I narrowed this down to choices A and D. I picked A because I thought the flaw was assuming one option had to happen because the other didn't. I'm not sure actually how A and D are different.

Could you please explain?
Thanks,
Candace

[Robert Carroll]

Candace,

The flawed argument in the stimulus begins by proposing two options, without saying that those options exhaust all possibilities. It then provides evidence for eliminating one option, and concludes by saying that the other option must be selected.

Answer choice (A) fails to eliminate a possibility in the premises. Instead, it gives a reason FOR one of the options, and CONCLUDES by eliminating the other. This does not parallel the flawed reasoning in the stimulus. Only answer choice (D) does this.

Robert Carroll

[candaceross]

Ohh okay, I see now!

Thank you very much Robert!

[graciekang]

hi im struggling bc i thought that the stimulus is flawed bc BOTH might me burglars, and NEITHER might be burglars. On that note, i thought (A) is the right answer bc the zoo might build primate house AND refurbish polar bear exhibit, and that matches the flaw of the stimulus. (D) is flawed bc NEITHER might be happening, but it cannot be the case that BOTH might be happening. So i thought (D) lacks one side of flaw.

I would appreciate it if you can explain why i should assume that the bulgar was only one person in the stimulus, which makes the possibility of BOTH being the burglar impossible.

[Jeff Wren]

Hi gracie,

The premise that states that "Schaeffer has an ironclad alibi" essentially rules out Schaeffer from being the burglar (and rules out that Schaeffer and Forster were both the burglars) for all intents and purposes. An "ironclad alibi" means an alibi that is too strong to be questioned or doubted.

The flaw in this argument, like most arguments, occurs in the shift from the premises to the conclusion. Just because Schaeffer was not the burglar (which has been established) does not prove that "Forster must be the burglar." Those two people may have been the only two suspects that the police department had, but that does not mean that they are in fact the only two people who could have committed the burglary.

As discussed in the complete question explanation, this argument contains a very specific type of flaw known as a false dilemma in which someone assumes that only two options are possible when there may be additional options. For example, arguing "we can't do A, so we must do B" when there may be many other options (C, D, E, etc.) that were not considered.

Notice how the stimulus provides two options or possibilities (Schaeffer and Forster), rules out one option (Schaeffer) and concludes that the other option must be true (Forster must be the burglar) even though other options (i.e. someone other than the two suspects committed the burglary) are certainly possible.

Answer D does the exact same thing and has the exact same flaw. Two options/possibilities are provided, one is ruled out, and the argument concludes that the other one must happen.

Answer A has a different flaw. Two options/possibilities are provided. There is good reason to believe that one of those will happen, and the argument concludes that the other one will not happen.

See the difference?

More information about flaws, including false dilemmas, can be found in "The Logical Reasoning Bible."