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#15 - The typological theory of species classification

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Complete Question Explanation

Flaw in the Reasoning. The correct answer choice is (C)

This stimulus presents a discussion of species classification. Under the typological theory, which is not widely used today, species are classified solely on the basis of observable physical characteristics, even though “sibling species” are indistinguishable on the basis of appearance. Because they cannot interbreed, the mainstream theory of species classification distinguishes these sibling species as separate species. The passage concludes that the typological theory of species classification is unacceptable because it does not recognize this distinction:

    Premise: ..... The typological theory, which classifies based on physical appearance, does not consider sibling ..... ..... ..... ..... species to be separate species, even though they cannot interbreed.

    Premise: ..... The mainstream theory of species classification does distinguish sibling species, based on the fact that ..... ..... ..... they cannot interbreed.

    Conclusion: ..... The typological theory must be unacceptable.

The question asks us to identify a weakness in the argument. The author bases the conclusion on the fact that the two theories have different perspectives, apparently presuming the exclusive validity of the mainstream theory.

Answer choice (A): The argument doesn’t require that all aspects of the typological theory be discussed. Since this does not weaken the writer’s conclusion, this answer choice is incorrect.

Answer choice (B):This answer choice describes a conditional reasoning error that is not reflected in the stimulus.

Answer choice (C): This is the correct answer choice. The author relies on the mainstream theory of classification (and presumes its merit) to discredit the typological theory—the need to recognize sibling species as separate species provides the basis of the argument advanced in the stimulus.

Answer choice (D): This would not necessarily be a flaw if it were accurate; a single fact is in some cases sufficient to determine a theory to be inaccurate. There is no such fact in this stimulus, however, so this answer choice is incorrect.

Answer choice (E): The author does not need to explain why sibling species cannot interbreed. Since this plays no role in the argument, this answer choice is incorrect.
Applesaid
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Hello!

I am freakingly bad at the type of question that asks things about "most vulnerable to." Although this is a flawed reasoning, I don't think I've gotten the key to decoding them.

Just like this one with complex stimulus, I think comprehending the passage itself is the key to get the right answer. However, even tho I thought I already well comprehend the passage I still got the answer choice wrong.

I paraphrase this passage as: because the typological theory of species classification distinguishes species solely on some basic observable facts, and there's an example of "sibling species" that are indistinguishable in typological theory, and the mainstream theory places them as separate species, thus typological theory is unacceptable.

According to your course instruction, prephrase is really important. Without looking at those answer choices, I thought this argument is flawed because it denies one theory based on a single example, and thus leading me to incorrectly choose the answer choice D.

I can understand why C is a correct one. However, I don't why D is incorrect. I bet it's because although D is a potential contender, it is inferior to C. Am I right?

Also, can anyone show me how to properly approach such kind of flawed reasoning question? And how to secure a correct answer choice when debating between 2 potentially correct answer choices? Thanks a lot. This type is my real weakness.
David Boyle
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Applesaid wrote:Hello!

I am freakingly bad at the type of question that asks things about "most vulnerable to." Although this is a flawed reasoning, I don't think I've gotten the key to decoding them.

Just like this one with complex stimulus, I think comprehending the passage itself is the key to get the right answer. However, even tho I thought I already well comprehend the passage I still got the answer choice wrong.

I paraphrase this passage as: because the typological theory of species classification distinguishes species solely on some basic observable facts, and there's an example of "sibling species" that are indistinguishable in typological theory, and the mainstream theory places them as separate species, thus typological theory is unacceptable.

According to your course instruction, prephrase is really important. Without looking at those answer choices, I thought this argument is flawed because it denies one theory based on a single example, and thus leading me to incorrectly choose the answer choice D.

I can understand why C is a correct one. However, I don't why D is incorrect. I bet it's because although D is a potential contender, it is inferior to C. Am I right?

Also, can anyone show me how to properly approach such kind of flawed reasoning question? And how to secure a correct answer choice when debating between 2 potentially correct answer choices? Thanks a lot. This type is my real weakness.


Hello,

There is probably no "magic trick" which will let you automatically choose between two contenders. Just keep doing flaw-in-the-reasoning questions and review the course materials so that you're familiar with all the kinds of flaws, and that may help develop your skills.

As for the problem: the thing about "sibling species" is more of an interpretation than a fact, so choice D, "the argument takes a single fact that is incompatible with a theory as enough to show that theory to be false", is not apposite. The sterility of "sibling species" works under typological theory, and all the species are considered the same because of appearance etc. And it works under the mainstream theory, where species are called different because of sterility. So a different interpretation, of the same facts.
The flaw, as noted in answer C, is that the stimulus calls the typological theory wrong just because it doesn't agree with the mainstream theory. But what if the mainstream theory is wrong instead?

David
Applesaid
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Hey David,

Thank you for your reply. But I am sorry. I still don't get why it is a matter of interpretation while I look at those sentences as factual statement. Could you please provide further explanation? When we read the stimulus, should we distinguish a statement of interpretation from factual statements in general?

Celine
Applesaid
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By the way, is D "taking a single fact that is incompatible with a theory as enough to show that theory to be false" equivalent with a case of "overgeneralization"? I am quite confused. :oops:

I still don't understand why it's not flawed in taking a single example to support a general claim ?
KelseyWoods
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Hi Celine!

So the flaw here is that the author is saying that just because the typological theory doesn't correspond to the mainstream theory, it must be unacceptable. But even though one of the theories is considered "mainstream" they are both still theories which means that neither one has been 100% proven. So couldn't the fact that the typological theory doesn't correspond to the mainstream theory be just as easily used to show that the mainstream theory is unacceptable? The fact that the two theories don't completely match one another doesn't prove or disprove either one. But the author, as answer choice (C) says, has assumed that the mainstream theory is correct and therefore thinks the incompatibility between them proves the typological theory is false.

Answer choice (D) does indeed describe an overgeneralization. But that's not the flaw we have here. Read (D) carefully....it says "takes a single fact that is incompatible with a theory as enough to show that theory to be false." Really what the stimulus author does is "takes a single component of one theory that is incompatible with another theory to prove that theory to be false."

As David says, we're not really dealing with facts, just interpretations based on two different theories. One theory interprets the sibling species as one species and the other interprets them as two separate species. But just because they don't agree in their interpretations doesn't prove that one of them is false.

Hope that clears things up!

Best,
Kelsey
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Hi Kelsey,

Thank you for your further clarification. I got it!

CC
actionjackson
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Administrator wrote:Complete Question Explanation

Flaw in the Reasoning.
The question asks us to identify a weakness in the argument. The author bases the conclusion on the fact that the two theories have different perspectives, apparently presuming the exclusive validity of the mainstream theory.

[b]Answer choice (C): This is the correct answer choice.
The author relies on the mainstream theory of classification (and presumes its merit) to discredit the typological theory—the need to recognize sibling species as separate species provides the basis of the argument advanced in the stimulus.

Answer choice (D): This would not necessarily be a flaw if it were accurate; a single fact is in some cases sufficient to determine a theory to be inaccurate. There is no such fact in this stimulus, however, so this answer choice is incorrect.


I was between C and D for this one, but I have a few questions about this question and its explanation. First, I thought we categorize this as a Flaw in the Reasoning question, however the explanation provided states that the question asks us to identify a weakness in the argument. Are the two similar enough that it doesn't really matter if the question is categorized as a Flaw or a Weaken (I mean I get that if you find the flaw you find the weakness but I'm pretty confused here)?
Also, before heading to the answer choices I said to myself, "Looks like an appeal to authority" ok, no luck with that in the answer choices. D. seemed to be describing to me an Evidence flaw; specifically that some evidence against a position is taken to prove that position as false. The explanation provided for D. which says this wouldn't necessarily be a flaw confuses me. Isn't this AC describing an error in the use of evidence? Some evidence presented against a position only weakens a position, it does not prove that position is false? Whereas what is C. describing, is it an assumption flaw? The stimulus never provided that the mainstream theory was true, just that the typological theory had an oversight and was therefore unacceptable. But by comparing the two theories in the premise(s), discussing the shortcoming of one, and then concluding something about only one the author is assuming the mainstream theory is acceptable? That there is some mutual exclusivity present? Any help figuring out what I'm missing here would be much appreciated. Thank you Powerscore.
Luke Haqq
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HI actionjackson!

Happy to try to help provide some clarity on this question.

First, you raise a good point about the similarity of "weakness" and "weaken" on the LSAT. But to your question, they are used in distinct question types. In this particular question you know it's a "Flaw in the Reasoning" question stem because of the phrasing "...the argument is most vulnerable to criticism on the grounds that."

"Identifying a weakness" is suppose to be synonymous with "Identifying a Flaw in the Reasoning." The answer choices listing those general flaws might include ad hominem arguments, circular arguments, bad data, etc.

By contrast, when you see a question stem asking what would "weaken/undermine" the argument, the answer choices are going to focus on the specific argument and conclusion, rather than such general flaws. For example, if the stimulus includes a causal argument, an answer choice might weaken it by showing an alternative cause, or by showing the causal relationship is reversed.


Second, to your discussion of answers (C) and (D). While (D) initially seemed plausible when I read it, to me it seems like a "shell game." That is, the answer choice starts off fine--"takes a single fact"--but the second part--"...as enough to show that theory to be false" seems problematic. The stimulus doesn't conclude that typological theory is "false" (the language used in (D)), only that it is "unacceptable."

(C) addresses the issue that the author of the stimulus assumes there's one metric for determining a theory's "acceptability," namely, whether the theory accounts for sibling species as separate species. But this is only a problem for those who accept "mainstream biological theory," since it is that mainstream theory that finds it necessary to differentiate sibling species. In other words, as (C) gets across, the author "presupposes the truth of an opposing theory" in attempting to refute typological theory.

Hope that helps!