LSAT PrepTest 144 - Section 1 - Passage 4 - Question 20

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Passage A.

Intro to Popper · Power of negative evidence

A single black swan disproves that all swans are white

Asymmetry · Between positive and negative evidence

Positive evidence has no value

Requirements of Science · Search for negative evidence; making falsifiable predictions

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Critique of Popper · Negative evidence is not as powerful as he believes

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Premise · Theories have to work together to entail predictions

So a failed prediction means some theory is false, but it's unclear which one.

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Prediction · Orbit of Uranus

Multiple theories working together to entail the predictions. This can be framed as an application of Passage A.

Prediction · Failed

At least one of the theories is wrong.

Explanation · There's another planet

Scientists discovered Neptune.

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Prediction · Orbit of Mercury

Prediction · Failed

Perhaps Newton's laws are incorrect or perhaps there's another planet.

Explanation · Newton's laws are incorrect

Einstein's general theory of relativity is more correct.

Passage Style

20.

Which one of the following ██ █ ███████ █████ ██ ████ █████████

Question Type

Main point

Split Approach: After passage A, eliminate any answer choice that doesn’t reflect the topic of passage A. Then, after passage B, choose the remaining answer choice that best reflects the topic of passage B (and of passage A).

Sequential Approach: Author A argues that negative evidence (observations that contradict a theory) isn’t as powerful or straightforward as Popper said. Author B gives an example of how negative evidence disproved an assumption in one case (observations of Uranus’s orbit contradicted scientists’ predictions because of a flawed assumption) and disproved a theory in another case (observations of Mercury’s orbit contradicted predictions because Newton’s theory was wrong). So both passages deal with the use of negative evidence in science.

the logical asymmetry ██ ████████ ███ ████████ ████████

This topic is dealt with in passage A but not passage B.

the role of █████████ ███████████ ██ ██████████ █████████ ██████

This topic isn’t dealt with in passage A.

the role of ████████ ████████ ██ ██████████ ████████

This is a central topic of passage A, which argues that negative evidence (observations that contradict a theory) isn’t as powerful as Popper said. This is also a central topi co passage B, which argues that negative evidence predicted the existence of Neptune (because observations of Uranus’s orbit contradicted theoretical calculations) and helped support the theory of relativity (because observations of Mercury’s contradicted Newton’s theory).

69%

the proper technique ███ ██████████ █ ██████████ ██████

Passage A is more about the challenges of confirming a scientific theory than about the “proper technique.” Author A never actually points the existence of a proper technique. She just says that negative evidence isn’t all it’s cracked up to be and things are more complicated. And passage B is too specific; it only looks at how one theory (Newton’s) was eventually replaced by another (Einstein’s) in part because of evidence about Mercury. It doesn’t get into what the “proper technique” is for confirming scientific theories in general.

21%

the irrelevance of ███████████████ ███ ██████████ █ ██████████ ██████

Author A doesn’t discuss the “irrelevance” of experimentation. She says that when experiments fail, it’s not always immediately obvious why. But she doesn’t take any stance on whether experiments are outright irrelevant. That’s enough to eliminate (E). Meanwhile, author B doesn’t discuss experimentation in the first place.

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PrepTest 144 - Section 1 - Passage 4 - Question 20

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PrepTest 144 - Section 1 - Passage 4 - Question 20

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