Reading comp PrepTest 144 · Section 1 · Question 24

Passage

 . Passage A  .       Karl Popper's main contribution to the philosophy  . of science concerns the power of negative evidence. Remaining source text redacted.
Passage walkthrough
Passage SummaryTopic: Science

Passage A
Paragraph 1
  • Paragraph note
    • A philosopher is introduced, and his theory is explained in depth, focusing on a distinction
  • Views, minor Meta-Structures, points of intersection, and the author's attitude
    • Popper - Theory of negative evidence (vs positive evidence)
    • Example - "All swans are white"
      • Positive evidence - white swans (can't prove all are white); Popper says no value
      • Negative evidence - black swan (one proves idea is wrong); Popper says disproves
    • Author - Popper's view "hyperbolic"
    • Popper - Negative evidence is core of science (scientific theory → makes predictions testable with negative evidence)
Paragraph 2
  • Paragraph note
    • The Author rebuts Popper's argument to some degree
  • Views, minor Meta-Structures, points of intersection, and the author's attitude
    • Author - Popper's view doesn't reflect scientific reality
    • False prediction, premise of theory is wrong
    • But which one? All theories have "auxiliary" premises from other theories and the real world (e.g., instruments work)
    • Author - Popper is right to say positive evidence isn't conclusive; wrong to say negative evidence is
Passage B
Paragraph 1
  • Paragraph note
    • A scientific situation is walked through
  • Views, minor Meta-Structures, points of intersection, and the author's attitude
    • Uranus orbit predictions were off, relied on Newton's laws, and auxiliary assumptions (including no other planets were nearby)
    • Predictions wrong, so a premise must have been wrong
    • Scientists tested other planets around, found that was the mistake
Paragraph 2
  • Paragraph note
    • A similar scientific situation is walked through
  • Views, minor Meta-Structures, points of intersection, and the author's attitude
    • Mercury orbit predictions were off, scientists predicted another planet (like with Uranus)
    • No planet found, Einstein's new laws matched up with reality, so scientists rejected Newton's theory
Main Point:
Passage A - Popper's philosophy of science doesn't reflect the reality scientists face, especially with respect to the certainty with which negative evidence can disprove theories.

Passage B - When predicting the orbit of Uranus, scientists were correct in predicting a new planet, but in a similar situation with Mercury, it was actually Newton's laws that were shown to be incorrect.

Key Lines:

Passage A:
Lines 3-5 - An example makes a distinction much clearer
Lines 6-10 - A view is clarified and the Author calls it exaggerated ("hyperbolic")
Lines 17-19 - The Author criticizes the opposing view
Lines 30-32 - The Author clarifies her view, showing a shared viewpoint and an opposed viewpoint with the opposing point

Passage B:
Lines 41-44 - Alternative possibilities are discussed
Lines 48-51 - One possibility is shown to be correct
Lines 53-54 - A similar situation is raised
Lines 58-64 - A different possibility is shown to be correct in this example, with implications for the first

Meta-Structure - Relationship Between Passages:
Rebuttal (Passage A) - The Author of Passage A clearly thinks that Popper's philosophical contribution isn't 100% correct. However, she does clarify this at the end. Popper claims that positive evidence is inconclusive, but negative evidence is definitive in disproving a claim. The Author agrees that positive evidence is inconclusive (though she disagrees with Popper's view that it lacks all value), but she disagrees that negative evidence is always conclusive.

Comparisons (Passage B) - Passage B brings up two similar situations—planets are discovered, their orbits are predicted, and those predictions are wrong. However, the outcome of these situations is different. In the Uranus situation, it ended up being an auxiliary assumption (no other planets in the area) that was wrong. In the Mercury situation, it ended up being Newton's theories that were wrong.

Neutral Author (Passage B) - The Author of Passage B doesn't really take any sides or show any opinion. Rather, he focuses on presenting the details of two separate situations.

How do these passages relate? In a complicated manner! The first passage discusses an approach to scientific inquiry that revolves around positive and negative evidence. How does this apply to the two situations in Passage B? Well, in the Uranus case, the scientists used what they knew to predict an orbit, and that orbit turned out to be wrong. In other words, they made a prediction, and the evidence proved that prediction wrong—negative evidence!

In the Mercury example, they predicted an orbit that turned out to be wrong, so that's more negative evidence. They also then made a prediction that, similar to the Uranus situation, there would be another planet, but they didn't find one—also negative evidence!

(This was a lot of analysis, and we almost certainly wouldn't have walked through all of this ahead of heading to the questions. It's here to help you wrap your head around the passages!)

Also important to note is that the Author of Passage A talks about "auxiliary" assumptions, and Passage B brings these up as a possible place for a prediction made by a theory to go wrong. That overlap aligns the approach in Passage B with that of the Author over Popper.

Last Thoughts:
This comparative set is rough. It's hard to understand, abstract, and definitely outside of most people's area of expertise. So what can you do to make it easier? Rely on that example in Passage A, Paragraph 1. If we can understand what positive and negative evidence is, we should be able to muddle through the detail questions. And as for the Authors' viewpoints, Passage A has some clear statements of opinion, and Passage B lacks a particularly present author.

Question prompt

The author of 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

  1. A
    the discovery of Uranus
    Why choice A is not credited
    Incorrect. Passage B starts by saying that the planet Uranus was discovered. However, this wasn't based on a theory or said to confirm or deny a theory, so it doesn't have to do with evidence, let alone negative evidence.
  2. B
    the initial failure of Remaining source text redacted.
    Why choice B matches the stem
    Correct. Question Type:
    Strengthen

    Strategy Overview:
    Review the last sentence of Passage A and understand what it means, then figure out what situation in Passage B would strengthen it

    Answer Anticipation/Relevant Lines:
    The last line in Passage A claims that "negative evidence rarely is" conclusive. So what is negative evidence again? It's evidence that disproves a prediction made by a theory. So the Author of Passage A is claiming that evidence disproving a prediction made by a theory doesn't always disprove the theory.

    Let's consider each of the situations described in Passage B to see where we can find an example of this, starting with Uranus.

    In that situation, the scientists made a prediction about the orbit of Uranus based on Newton's laws and assumptions about the mass of various celestial objects and a lack of other planets. This orbit turned out to be wrong—so there was evidence that proved a prediction based on a theory wrong. And while one explanation was that Newton's theories were wrong, another was that an auxiliary assumption was. That's what they ran with, and they found Neptune, which lined up with Newton's theories to explain Uranus's orbit.

    So, in other words, there was negative evidence against Newton's theories, but that didn't end up disproving that theory. That backs up the Author's claim at the end of Passage A that negative evidence is rarely conclusive. (Note that Newton's theories would go on to be disproven in the next example, but the negative evidence here didn't manage to knock it out, so this counts.)

    What about the Mercury situation? There, again, Newton's theories were used to make a prediction about Mercury's orbit that ended up being wrong—negative evidence. However, in this example, Newton's theories were rejected and replaced with Einstein's, so the negative evidence was conclusive.

    So we're looking for the first situation we described as an answer—the fact that Newton's theories didn't correctly predict Uranus's orbit but ended up being vindicated when Neptune was discovered.

    Answer Explanation:
    (Lines 41-44; 48-51) Newton's laws predicted a certain orbit for Uranus, but that orbit ended up being wrong. That's negative evidence for Newton's laws. However, it ended up that the prediction was wrong because scientists weren't aware Neptune existed. When they assumed another planet existed, Newton's laws worked out the correct orbit, and then Neptune was discovered where those laws predicted it would be found. So the initial negative evidence against Newton's theories ended up instead leading to the discovery of Neptune and an orbit that lined up with Newton's laws. As such, this is an example of negative evidence not conclusively proving a theory to be wrong, so this is the correct answer.

    Key Takeaway:
    Phew, what a question. Something like this needs to be tackled piece by piece. First, clearly define the sentence you're trying to strengthen. Second, figure out what it means (here, that just because a piece of evidence disproves a prediction made by a theory doesn't mean that the theory can be ruled out). Third, find an example of it. Don't be afraid to break these questions up into steps to make them more manageable!
  3. C
    the ultimate failure of Remaining source text redacted.
    Why choice C is not credited
    Incorrect. (Line 62) This failure led to the rejection of Newton's theory of gravity, which is an example of negative evidence (the failure of Newton's laws to predict Mercury's orbit) conclusively proving a theory wrong. That doesn't line up with the contention at the end of Passage A that negative evidence is rarely conclusive.
  4. D
    the failure to find Remaining source text redacted.
    Why choice D is not credited
    Incorrect. (Line 62) The failure to find Vulcan was part of the example that ended up leading to the rejection of a theory, whereas the end of Passage A talks about situations where theories can't be rejected despite negative evidence. And even if we consider Vulcan's existence to be a theory, the failure to find it isn't noted as failing to disprove its existence.
  5. E
    the success of Einstein's Remaining source text redacted.
    Why choice E is not credited
    Incorrect. (Lines 63-64) The correct prediction of Einstein's general theory of relativity to predict the orbit is positive evidence, and it's noted that this "increased confidence" in that theory. So it does seem as if this example strengthens the contention that positive evidence isn't conclusive (since the passage doesn't say that it proved Einstein's theory, just increased confidence in it), but the question is about the last sentence—which is about negative evidence. This answer might strengthen the second to last sentence.

What this tests

Question analytics

Based on historical answer selection rates for this question.

Answer choice distribution

  1. A 4%
  2. B Credited 39%
  3. C 19%
  4. D 32%
  5. E 6%

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