Self-study
Passage A.
P1
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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
P2
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Critique of Popper ·
Negative evidence is not as powerful as he believes
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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P3
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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.
P4
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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
25.
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a
Mercury
The black swan is an example of negative evidence that disproves the theory that all swans are white. We want something analogous: an example of negative evidence that helped to disprove Newton’s theory. Mercury is a great example. Mercury’s orbit didn’t match what Newton’s theory predicted, which made Mercury itself negative evidence against Newton’s theory. This ultimately led to the disproving of Newton’s theory. So Mercury is analogous to the black swan.
b
Uranus
The black swan is an example of negative evidence that disproves the theory that all swans are white. We want something analogous: an example of negative evidence that helped to disprove Newton’s theory. But Uranus was positive evidence in support of Newton’s theory. (Once Neptune was accounted for, Uranus’s orbit perfectly matched what Newton’s theory predicted.)
c
Neptune
The black swan is an example of negative evidence that disproves the theory that all swans are white. We want something analogous: an example of negative evidence that helped to disprove Newton’s theory. But Neptune wasn’t negative evidence against Newton’s theory. To the contrary, Neptune saved Newton’s theory by offering an alternative hypothesis for why Newton’s theory initially failed to predict the orbit of Uranus. (It wasn’t that Newton’s theory was wrong; it was just that scientists overlooked the existence of Neptune. Once they accounted for Neptune, their observations matched Newton’s theories.)
d
Venus
Venus isn’t mentioned in passage B. We’re looking for something in mentioned in passage B that’s analogous to the black swan in passage A.
e
the sun
The black swan is an example of negative evidence that disproves the theory that all swans are white. We want something analogous: an example of negative evidence that helped to disprove Newton’s theory. But the sun didn’t help to disprove Newton’s theory.