LSAT 142 | Section 1 | Logical Reasoning: Q19

QUESTION TEXT: If temperatures had dropped below freezing when I was…

QUESTION TYPE: Parallel Reasoning

CONCLUSION: Temperatures didn’t go below freezing last week.

REASONING: Freezing ➞ impatiens dead ➞ bloom

Contrapositive: bloom ➞ impatiens dead ➞ freezing

The impatiens did bloom.

ANALYSIS: This argument uses a valid chain of conditional statements. We can say that if temperatures were below freezing last week, the impatiens would not have bloomed. The contrapositive above shows that since the impatiens did bloom, temperatures didn’t go below freezing.

The right answer must copy these features of the argument:

1. Combines two conditional statements
2. Takes the contrapositive
3. Uses a fact to prove something with the contrapositive.

The answers are long. You shouldn’t read them. Skim them, and look for the structural features above. Here’s my quick skim
A: Has two conditionals. Contender.
B: Second sentence says “some”. Eliminate.
C: Doesn’t use any facts, only conditionals. First sentence is “if but only if”. Eliminate.
D: Says “should”. That’s a moral question. Eliminate.
E: Says “should”. That’s a moral question. Eliminate.
Note that the LSAT strictly separates fact and morality. Answers with “should” are highly unlikely to be parallel if the stimulus is fact based.

This process left A. I then considered it more carefully, and saw it matched. Note that B-E are just soft eliminates. If A were wrong, I’d have to look at them again.

Notes on Skimming: You should practice skimming parallel reasoning answers for structure. The right question is not “how could I eliminate this” but rather “how could I eliminate this in 2-3 seconds?”.

Like any other skill in life, you’ll get better at this if you practice identifying the structure of the stimulus and then using that to eliminate wrong answers fast. Make a collection of long parallel reasoning questions, and redo them periodically to practice.

Note that it takes a lot of words to explain how I do this type of question. But it doesn’t take me long to do this type of question, because I don’t have to justify myself to anyone. A question like this one can be answered in 30 seconds.

___________

1. CORRECT. This exactly parallels the structure: Adaptable ➞ Thrive ➞ Adverse
   Adverse ➞ Thrive ➞ Adaptable
   The species has had no adverse effect, therefore it’s not adaptable.
2. The first sentence is fine. The second sentence is wrong: it gives a “some” statement. This answer also makes a switch between being adaptable and actually adapting to a new environment. Those are different things, and the stimulus didn’t make that distinction.
3. This is a flawed argument, and it has a different structure from the stimulus. Here’s how to draw the first sentence:
   Introduced AND Adapt ➞ Adverse affect
   The conclusion says that if a species doesn’t adapt, then there will be no adverse effect. That’s incorrectly negating a sufficient condition. Necessary conditions can happen without sufficient conditions.
4. This is a good argument, but it’s just a single conditional statement, with a fact. This also includes “should” which introduces a moral element absent from the stimulus. Here’s the one conditional: Adverse effect ➞ should not introduce
   The conclusion just follows the conditional by saying an adverse effect will be present, therefore the species shouldn’t be introduced.
5. This answer is just a confused jumble of words. The first sentence doesn’t link to anything. It tells us not to introduce species if they cause harm, but then the third sentence says that species will be introduced anyway. The second and third sentence just say, without proof, that we ought to control populations. (The benefit is that the risk of adverse impact is limited, but we don’t know if there are any drawbacks to manual population control).

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