PrepTest 140
[lcid:3659] Prep Test 140 LSAT — Reading Comp — S4
Reading comp
Passage
Questions 20-27 . Physicists are often asked why the image of an . object, such as a chair, appears reversed
Remaining source text redacted.
Passage walkthrough
Passage SummaryTopic: Science
Paragraph 1
While the appeal of the "front-to-back" theory of how mirrors work is understandable, it ultimately fails because a correct explanation needs to include both the mirror and the person looking into it.
Key Lines:
Lines 1-4 - The question/phenomenon is brought up
Lines 4-7 - A first explanation is presented
Lines 14-16 - A second explanation is presented
Lines 21-23 - The Author points out a flaw in the second explanation
Lines 26-27 - The Author explores the appeal of the second explanation
Lines 42-44 - The Author explores another reason for the appeal of the second explanation
Lines 48-51 - The Author states her conclusion about what a proper theory of mirrors must do
Meta-Structure:
Phenomenon/Explanation (or Question/Answer, which is very similar) - Here, the phenomenon is the "reversed" image in mirrors, the question, why does that happen? One explanation is that it reverses around the human field-of-sight axis. Another is that it reverses things front-to-back, but the Author says this is "based on a false premise" (Lines 22-23). Finally, the Author concludes that a proper explanation needs to take both the observer and what mirrors do into account.
Last Thoughts:
First, this is a notoriously difficult passage, so if you struggled, you're in good company! When that happens, rely on the structure and statements of opinion. Those two things will help you get through the difficult passages.
The first paragraph is a little confusing, so we should expect some questions on that—we'll need to head back to figure out what the correct answer is for any questions dealing with the concept of field of sight axes and rotation.
One thing that's absolutely important to think about—the Author's closing statement, where we finally learn her opinion on the subject of explaining mirrors. While two theories are presented, the Author concludes not with the acceptance of one theory over the other, but rather with the adoption of a criterion by which theories should be judged. She concludes that a theory is valid "only if we consider both what mirrors do and what happens when we look into mirrors" (Lines 49-51).
How does this apply to the two theories? We know that she pointed out an appeal of the second theory (the Reverse Image theory) is that it cuts out the observer, so she believes that theory isn't a good one (which lines up with her stating it relies on a false premise). The first theory does rely on the observer to explain how a mirror works—it relies on human vision featuring a vertical axis, explaining the left-to-right reversal. But just because it matches up with a requirement for a valid theory doesn't mean the Author accepts it—she never explicitly does, so we have to be careful about selecting answers that are too accepting of that theory.
Paragraph 1
- Paragraph note
- A question/phenomenon is introduced, along with an answer/explanation
- Views, minor Meta-Structures, and the author's attitude
- Phenomenon - Mirrors reverse images left-to-right instead of top-to-bottom
- Explanation - "Field-of-Sight" explanation - the reversal reflects how human field of sight is rotated (vertical axis)
- Base example - Chair
- Paragraph note
- Another answer/explanations is presented, and the Author gives an opinion on it
- Views, minor Meta-Structures, and the author's attitude
- Explanation 2 - Mirrors reverse front-to-back, which makes sense if you think about the reflected chair as being inside the mirror
- Problem with Explanation 2 - Most notable: Based on false premise, since the "chair" inside the mirror isn't real
- Paragraph note
- Why Explanation 2 is appealing
- Views, minor Meta-Structures, and the author's attitude
- It makes sense with our senses, since we "see" the chair in the mirror and thus think of it as real
- Example - We don't focus on mirrors but on objects in them
- Paragraph note
- Another reason Explanation 2 is appealing, with the Author's rebuttal
- Views, minor Meta-Structures, and the author's attitude
- Scientists try to explain without referring to observer
- Author - When you're trying to explain an observation, you need the explanation to include the observer
While the appeal of the "front-to-back" theory of how mirrors work is understandable, it ultimately fails because a correct explanation needs to include both the mirror and the person looking into it.
Key Lines:
Lines 1-4 - The question/phenomenon is brought up
Lines 4-7 - A first explanation is presented
Lines 14-16 - A second explanation is presented
Lines 21-23 - The Author points out a flaw in the second explanation
Lines 26-27 - The Author explores the appeal of the second explanation
Lines 42-44 - The Author explores another reason for the appeal of the second explanation
Lines 48-51 - The Author states her conclusion about what a proper theory of mirrors must do
Meta-Structure:
Phenomenon/Explanation (or Question/Answer, which is very similar) - Here, the phenomenon is the "reversed" image in mirrors, the question, why does that happen? One explanation is that it reverses around the human field-of-sight axis. Another is that it reverses things front-to-back, but the Author says this is "based on a false premise" (Lines 22-23). Finally, the Author concludes that a proper explanation needs to take both the observer and what mirrors do into account.
Last Thoughts:
First, this is a notoriously difficult passage, so if you struggled, you're in good company! When that happens, rely on the structure and statements of opinion. Those two things will help you get through the difficult passages.
The first paragraph is a little confusing, so we should expect some questions on that—we'll need to head back to figure out what the correct answer is for any questions dealing with the concept of field of sight axes and rotation.
One thing that's absolutely important to think about—the Author's closing statement, where we finally learn her opinion on the subject of explaining mirrors. While two theories are presented, the Author concludes not with the acceptance of one theory over the other, but rather with the adoption of a criterion by which theories should be judged. She concludes that a theory is valid "only if we consider both what mirrors do and what happens when we look into mirrors" (Lines 49-51).
How does this apply to the two theories? We know that she pointed out an appeal of the second theory (the Reverse Image theory) is that it cuts out the observer, so she believes that theory isn't a good one (which lines up with her stating it relies on a false premise). The first theory does rely on the observer to explain how a mirror works—it relies on human vision featuring a vertical axis, explaining the left-to-right reversal. But just because it matches up with a requirement for a valid theory doesn't mean the Author accepts it—she never explicitly does, so we have to be careful about selecting answers that are too accepting of that theory.
Question prompt
According to the passage,
Remaining source text redacted.
Why the credited answer is right
Credited answer: B
The notes below walk through why it fits the stem and how to eliminate the rest.
Question Type
Science
Answer choices
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Aaccept the top-to-bottom explanation Remaining source text redacted.
Why choice A is not credited
Incorrect. (Lines 48-51) The Author isn't on board with the front-to-back theory, so the purpose of any statement in the argument can't be to help us accept that theory. There's a subtle difference between explaining why a theory is so appealing and arguing in favor of that theory, but that difference is present here. -
Bunderstand the front-to-back explanation Remaining source text redacted.
Why choice B matches the stem
Correct. Question Type:
Must Be True
Strategy Overview:
Find this section of the passage and the answer to this question
Answer Anticipation/Relevant Lines:
This question can be difficult to approach, as it talks about "mental constructs," and it would have been easy to overlook that specific phrase. However, it also asks about our sense perceptions. We noted these as a part of Paragraph 3, and you should have noted at least one of these two phrases as it was directly related to the point of the second paragraph—an explanation of why the front-to-back explanation is appealing.
So we should head back to that paragraph! And we just reminded ourselves that the purpose of that paragraph was to highlight the appeal of the front-to-back explanation. Lines 28-31 is where the topic of this question stem is discussed, and there it states that the way we deal with mental constructs/primary sense perceptions makes the front-to-back explanation "seem[] natural" since it's "quite successful" at explaining what mirrors do. Let's find an answer reflecting that.
Answer Explanation:
(Lines 27-28) The passage notes that the front-to-back theory is appealing because it's "quite successful" at explaining what a mirror does. The way we deal with mental constructs and our primary sense perceptions makes that theory "seem[] natural," which means that relying on our natural way of approaching this subject lines up with the front-to-back explanation, and thus helps to explain it. This is therefore the correct answer.
Key Takeaway:
These Must Be True questions that reference specific topics can be tough if you didn't leave a note on the specific topics, meaning you'd need to go on a wild goose hunt through the passage to find it! A good way to review such a question is to come up with a rule of thumb you can use in the future in order to note such a topic. Here, the fact that it answered an implicit question in the paragraph (why is this theory so appealing?) should have been a reason to note it. -
Cchallenge complex explanations of Remaining source text redacted.
Why choice C is not credited
Incorrect. There's no mention of any explanation here being "complex." The left-to-right theory just relies on us knowing that our heads usually turn left to right when viewing things! -
Dreject customarily reliable equations Remaining source text redacted.
Why choice D is not credited
Incorrect. (Lines 32-34) The passage notes that "[i]n general," we can equate mental constructs with primary sense perceptions, so being used to dealing with one wouldn't help us in rejecting that equation. If anything, it would make it more difficult! -
Eoveremphasize the fact that Remaining source text redacted.
Why choice E is not credited
Incorrect. This answer has complicated language that isn't mirrored in the passage. Since the question is asking about what is true "[a]ccording to the passage," we need something more closely tied into the language in the passage.
What this tests
Discussion
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Started by FS101