Section Types Logical Reasoning

LSAT 109 - Section 4 - Question 20

October 14, 2012

LSAT 22 - Section 4 - Question 26

October 14, 2012

LSAT 109 - Section 4 - Question 26

October 14, 2012

A member of the British Parliament is reputed to have said, “The first purpose of good social reform is to increase the sum total of human happiness. So, any reform which makes somebody happy is achieving its purpose. Since the reform I propose would make my constituents happy, it is a good social reform.”

Summarize Argument

The member of Parliament claims his proposed social reform is a good one. Why? Because it will make his constituents happy, and since social reform is meant to increase human happiness, any reform must be achieving its purpose if it makes at least one person happy.

Notable Assumptions

The member of Parliament assumes any reform that makes at least one person happy must increase the total happiness of humans, and that any reform is good if it achieves its purpose.

A

Different things make different people happy.

This is fully compatible with the member of Parliament’s argument. By his reasoning, his reform will be good even if it only makes his constituents happy.

B

The proposed reform would make a few people happy, but would not increase the happiness of most other people.

This does not challenge the assumption that a reform will increase total human happiness if it makes at least one person happy. The proposed reform may make some people happy and leave everyone else unaffected, in which case it would be a good reform by his rule.

C

The proposed reform would affect only the member of Parliament’s constituents and would make them happy.

This strengthens the argument. If the only people affected by the reform are those it makes happier, then the proposed reform really does increase human happiness in total.

D

Increasing some people’s happiness might not increase the sum total of human happiness if others are made unhappy.

This challenges a key assumption—that any reform that makes somebody happy must make people happier overall. The proposed reform might decrease total human happiness, even if it pleases the member’s own constituents.

E

Good social reforms usually have widespread support.

This does not say a good reform must be popular. Nowhere does the member of parliament argue his reform would be good because it receives widespread support.

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LSAT 23 - Section 3 - Question 18

October 14, 2012

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LSAT 24 - Section 2 - Question 10

October 14, 2012

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LSAT 101 - Section 2 - Question 10

October 14, 2012

Economist: The economy seems to be heading out of recession. Recent figures show that consumers are buying more durable goods than before, indicating that they expect economic growth in the near future.

Summarize Argument

The economist tells us that the current recession appears to be ending. To support this, we get a chain of reasoning. First, a fact: consumers have started purchasing more durable goods. Second, an interpretation based on this fact (i.e. a sub-conclusion): consumers expect economic growth soon. And with this, the economist supports the conclusion that the recession seems to be ending.

Identify Argument Part

The claim that consumers are buying more durable goods than before is a factual premise. More specifically, it is a premise that supports a sub-conclusion (consumers expect economic growth), which then supports the main conclusion (the recession is ending).

A

It is the phenomenon that the argument seeks to explain.

The argument isn’t really trying to explain a phenomenon. Instead, the economist is trying to make a prediction about the future based on current data. This answer choice just isn’t accurate to the argument.

B

Its truth is required in order for the argument’s conclusion to be true.

The conclusion that the recession seems to be ending may be supported by the claim about consumers’ purchases, but that doesn’t mean one is required for the other. The economist could be mistaken about the consumers but the conclusion could still be true.

C

It is an inference drawn from the premise that the recession seems to be ending.

Like (D), this gets things backwards: the claim that the recession seems to be ending is the main conclusion, not a premise. Also, the claim about consumers’ purchases is stated as a fact, not inferred from something else.

D

It is an inference drawn from the premise that consumers expect economic growth in the near future.

Like (C), this gets things backwards: the claim about consumers’ expectations is a sub-conclusion supported by the claim about consumers’ purchases. Also, the claim about consumers’ purchases is a factual premise, not an inference.

E

It is the primary evidence from which the argument’s conclusion is drawn.

This accurately describes the role of the claim about consumers’ purchases. It’s the only pure factual premise in the argument, meaning it’s our only piece of hard evidence. The rest of the argument is just a series of inferences drawn from this evidence.

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LSAT 24 - Section 3 - Question 11

October 14, 2012

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LSAT 101 - Section 3 - Question 11

October 14, 2012

Special kinds of cotton that grow fibers of green or brown have been around since the 1930s but only recently became commercially feasible when a long-fibered variety that can be spun by machine was finally bred. Since the cotton need not be dyed, processing plants avoid the expense of dyeing and the ecological hazards of getting rid of leftover dye and by-products.

Summary

Special cotton from green/brown fibers havae been around since 1930s. Only recently, this special cotton became commercially feasible when a long-fibered kind that can be spun by machine came about. This long-fibered kind doesn’t need to be dyed, which is why processing plants don’t need to spend money on dyeing. In addition, since the long-fibered variety doesn’t need to use dyes, plants don’t need to get rid of leftover dye from processing, which avoids some ecological damage.

Very Strongly Supported Conclusions

There’s no obvious conclusion to draw from these facts. I’d go into the answers thinking, “There are at least some advantages to the long-fibered variety of cotton from green/brown fibers over the non-long-fibered variety of that cotton.” But the correct answer could be unexpected.

A

It is ecologically safer to process long-fibered cotton than short-fibered cotton.

We know that the long-fibered green/brown cotton doesn’t have a certain ecological risk (because it doesn’t require dyes). But this doesn’t extend to long-fibered cotton that isn’t green/brown. We don’t know about ecological risks of other kinds of long cotton.

B

Green and brown cottons that can be spun only by hand are not commercially viable.

Strongly supported, because the green/brown cotton “only recently” became commercially feasible, and this happened after a variety that could be machine-spun “finally” came about. This suggests that before a machine-spun version came about, it wasn’t commercially viable.

C

Hand-spun cotton is more ecologically safe than machine-spun cotton.

We don’t get a comparison concerning ecological damage between machine-spun vs. hand-spun cotton. All we know about ecological risk is that if you don’t have to use dyes, you avoid at least one ecological risk.

D

Short-fibered regular cottons are economically competitive with synthetic fabrics.

We don’t get any comparison between short-fibered cottons and synthetic fabrics.

E

Garments made of green and brown cottons are less expensive than garments made of regular cotton.

We know that processing plants don’t need to spend on dyes for creating green/brown cotton. This doesn’t suggest that clothes from green/brown cotton are less expensive, however. There are many other costs that go into clothing; we can’t go from the lack of one specific cost with respect to the cotton to a claim about overall cost of clothing from the green/brown cotton compared to other clothing.

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LSAT 25 - Section 2 - Question 21

October 14, 2012

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LSAT 102 - Section 2 - Question 21

October 14, 2012

If this parking policy is unpopular with the faculty, then we should modify it. If it is unpopular among students, we should adopt a new policy. And, it is bound to be unpopular either with the faculty or among students.

Summary

If the policy’s not popular with faculty, then we should modify it (or, by contrapositive, if we shouldn’t modify the policy, then it must be popular with faculty).

If the policy’s popular with faculty, it’s bound to be unpopular with students. (And if it’s popular with students, it’s bound to be unpopular with faculty. Popularity with one group implies unpopularity with the other.)

If the policy’s not popular with students, we should adopt a new policy.

Notable Valid Inferences

If we shouldn’t modify the existing policy, we should adopt a new policy.

If the policy’s popular with faculty, we should adopt a new policy.

If the policy’s popular with students, we should modify the policy.

A

We should attempt to popularize this parking policy among either the faculty or students.

The stimulus doesn’t suggest that any one scenario is more desirable than another. There’s no indication that the existing policy should be popular with either group, or that there’s something undesirable about the policy being unpopular.

B

We should modify this parking policy only if this will not reduce its popularity among students.

This says that modifying the policy is sufficient for not reducing its popularity among students. There are two problems here. First, modifying the policy isn’t sufficient for anything. Second, the policy is either popular or unpopular—there’s no “reduce popularity” condition.

C

We should modify this parking policy if modification will not reduce its popularity with the faculty.

The sufficient condition here is never addressed in the stimulus. The stimulus only considers what happens when the policy is popular or unpopular. There’s no discussion of reductions in popularity.

D

If this parking policy is popular among students, then we should adopt a new policy.

The stimulus states that if the policy is unpopular among students, then we should adopt a new policy. Meanwhile, if the policy is popular as (D) says, we can infer that we should modify the existing policy.

E

If this parking policy is popular with the faculty, then we should adopt a new policy.

If the policy is popular with faculty, then it must be unpopular with students (because it’s bound to be unpopular with at least one group). And if it’s unpopular with students, then we should adopt a new policy.

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