LSAT 124 – Section 3 – Question 17

LSAT 124 - Section 3 - Question 17

December 2007

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Question QuickView	Type	Tags	Answer Choices	Curve	Question Difficulty	Psg/Game/S Difficulty	Explanation
PT124 S3 Q17	+LR	Flaw or descriptive weakening +Flaw Analogy +An	A 78% 165 B 2% 155 C 10% 158 D 9% 162 E 1% 159	131 146 160	+Medium	145.896 +SubsectionMedium

J.Y.’s explanation

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Lawyer: A body of circumstantial evidence is like a rope, and each item of evidence is like a strand of that rope. Just as additional pieces of circumstantial evidence strengthen the body of evidence, adding strands to the rope strengthens the rope. And if one strand breaks, the rope is not broken nor is its strength much diminished. Thus, even if a few items of a body of circumstantial evidence are discredited, the overall body of evidence retains its basic strength.

takes for granted that no items in a body of circumstantial evidence are significantly more critical to the strength of the evidence than other items in that body

If there were some items of evidence that were much more important to the overall strength, then losing even just a few of these items might reduce the overall strength significantly. So the author must assume that there’s no items that are much more important than the others.

presumes, without providing justification, that the strength of a body of evidence is less than the sum of the strengths of the parts of that body

The author assumes the opposite — that the strength of a body of evidence is more than the sum of the individual strengths of items in that body. This is why the author thinks losing a few items won’t affect the overall strength.

fails to consider the possibility that if many items in a body of circumstantial evidence were discredited, the overall body of evidence would be discredited

The author’s conclusion concerns what happens if “a few” items of evidence are discredited. This doesn’t imply any belief about what happens is “many” items are discredited. “Many” means a lot — “a few” doesn’t necessarily encompass “many.”

offers an analogy in support of a conclusion without indicating whether the two types of things compared share any similarities

The author does indicate that the two things compared are similar. Just as adding strands to a rope strengthens the rope, adding items of evidence strengthens the body of evidence.

draws a conclusion that simply restates a claim presented in support of that conclusion

(E) describes circular reasoning. The conclusion is not a restatement of any of the premises. The conclusion concerns what happens if a few items of evidence are discredited; none of the premises refer to this situation.

The question stem reads: The reasoning in the lawyer's argument is most vulnerable to criticism on the grounds that the argument… This is a Flaw question.

The lawyer begins by making an analogy. He claims that a body of circumstantial evidence is similar to a rope. He claims that each piece of evidence is like a strand in that rope: just as adding more strings to the rope makes a rope stronger, adding more pieces of evidence strengthens the body of evidence. He then describes how if a strand of a rope is broken, the rope does not break, and it still retains much of its strength. He concludes that, similarly, if you discredit ("break") a few pieces of evidence, the overall body of evidence is still strong.

When analyzing an argument that uses an analogy, a good first step is to ask yourself, "Are the two things being compared actually similar?" As you increase the points of difference between the two things being compared, the analogy's strength diminishes. In this case, we want to determine where the lawyer's analogy between ropes and bodies of evidence frays apart. The idea that adding pieces of evidence to the body increases the strength of the body, like adding strands to a rope, makes sense and seems like a pretty good point of comparison. However, the analogy fails when we consider the fact that strands of rope are all the same. However, not all pieces of evidence are equal: some add much more strength than others. You have experience with this on the LSAT. Take away a premise that strengthens the argument, and the argument can survive. Take away a premise necessary to the argument, and the argument falls apart. So if we took away a few pieces of necessary evidence, the body would fall apart. However, that is contrary to the lawyer's conclusion. If you didn't see this, that is ok! When doing POE, prioritize answer choices that draw a distinction between ropes and bodies of evidence.

Correct Answer Choice (A) is what we discussed. The lawyer takes for granted that no evidence is more important to the body than others.

Answer Choice (B) is wrong. If you picked (B), you likely had trouble determining what (B) means. (B) says to take the strength of each piece of evidence independently and add them up. That will be greater than the strength of the evidence if you take the pieces altogether. If anything, the opposite is true: adding many pieces of circumstantial evidence together tends to count as better evidence than taking each individually.

Answer Choice (C) is not a problem for the argument. If you interpret "many = few": The point of the lawyer's argument is to show that if you take away some strands of evidence, then the body retains its strength, so the possibility is addressed. If you interpret "many"> few": then sure, the possibility is ignored. However, that is not a problem for the argument because the lawyers' conclusion is limited to taking away a few pieces of evidence. Either way, the argument is not flawed because of (C).

Answer Choice (D) is tempting, but we run into problems with the word "any." The lawyer has indicated that bodies of evidence share similarities to ropes. Adding more pieces of evidence or strands increases the strength of both.

Answer Choice (E) is incorrect. The lawyer does not use his own premise as a conclusion.

LSAT 124 – Section 3 – Question 17

LSAT 124 - Section 3 - Question 17

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J.Y.’s explanation

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LSAT PrepTest 124 Explanations

Section 1 - Logical Reasoning

Section 2 - Logical Reasoning

Section 3 - Logical Reasoning

Section 4 - Reading Comprehension

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