3.14 - Parallel Flaw

Next we're learning all about Parallel Flaws. These questions are a variation of Parallel Reasoning that often tell you explicitly that there was a flaw in the argument.

Be careful, though. Not all Parallel questions will call out flawed reasoning. It's still up to you to understand the argument, including whether or not it's valid.

They tend to look like this:

• The flawed pattern of reasoning in the argument is most similar to that in which one of the following?
• Which one of the following arguments contains flawed reasoning that is most parallel to that in the argument?
• Which one of the following arguments is most similar in its flawed reasoning to the argument?

Your job on Parallel Flaws is to find the answer choice that makes the same error as the passage.

Like Parallel Reasoning, success boils down to your ability to identify argument parts and understand how they work together. And, like Flaw questions, there's the added element of identifying and matching up errors in reasoning.

Let's work through some sample questions.

Examples

June 2007 PrepTest, Section 2, Question 2

Let's start off with an easy one. This is Question 2 from Test J, Section 2:

All Labrador retrievers bark a great deal. All Saint Bernards bark infrequently. Each of Rosa's dogs is a cross between a Labrador retriever and a Saint Bernard. Therefore, Rosa's dogs are moderate barkers.

Let me get this straight. 100% of Labrador retrievers bark a lot. 100% of Saint Bernards bark a little. Rosa's dogs are Lab/Saint Bernard mutts. So they're moderate barkers? What?

That would be like saying, "All baseball players wear long pants. All basketball players wear shorts. I play both sports. So I wear capris." That makes no sense!

We have a great example of a similarly flawed argument in mind, so let's find our match in the answer choices.

Answer B gets us there. It reads, "All type A chemicals are extremely toxic to human beings. All type B chemicals are nontoxic to human beings. This household cleaner is a mixture of a type A chemical and a type B chemical. Therefore, this household cleaner is moderately toxic." Bingo.

Looking for a breakdown answer-by-answer? Check the link above to read our explanation.

June 2007 PrepTest, Section 3, Question 20

Here's another, Question 20 from Test J, Section 3:

We should accept the proposal to demolish the old train station, because the local historical society, which vehemently opposes this, is dominated by people who have no commitment to long-term economic well-being. Preserving old buildings creates an impediment to new development, which is critical to economic health.

This author seems to say, "We should demolish the old train station and stick it to those uneconomic old fogies." This isn't countering anything about the historical society's arguments. It's attacking their motivations. Ad hominem 101.

We're looking for an answer that says something like, "I don't like you/what you believe, so we shouldn't follow your advice." That's my prediction.

C's the only answer that involves an ad hominem attack. It suggests that we should go against beauticians' advice to get two haircuts a month because they're incentivized to give more haircuts. That's our answer.

Looking for the full explanation for this question? Follow the link above.

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That does it for Parallel Flaws. Join us next time as we learn to tackle Necessary Assumptions.