#24 - Specific Reference, Must Be True, Author's Perspective

[amydg]

I get that you want an answer that says negative evidence is rarely conclusive and I was stuck between B and C which both involved failure of Newton's Law but was unsure as to what role the initial or ultimate part played. I ended up choosing C which is incorrect. What is the reasoning to get B?

[Emily Haney-Caron]

Hi Amy,

Good question. For this question, the key is to not take the last sentence of Passage A in isolation, but rather to consider the context (the three sentences before it). That can help clarify that we're not just looking for an answer where negative evidence is not conclusive, but where one of the premises is false when a prediction fails. That leads us to B over C. Does that help?

[mN2mmvf]

Why not answer (D)? That seems like an example of negative evidence -- i.e., the fact that Vulcan was never found was a reason to doubt Newton's laws (but not sufficient to immediately disprove them).

[Francis O'Rourke]

This question is asking us to determine which example shows negative evidence leading to multiple possible conclusions.

After scientists saw Uranus's orbit seemed to go against Newtonian predictions, they had two possible conclusions: Newton's laws are incorrect, or there was an error in auxiliary assumptions. This is a clear example of "more than one possible explanation."

The non existence of Vulcan led some scientists to doubt Newton and ultimately led to only one conclusion: Newton was wrong. We are not told that there were multiple possible conclusions drawn from the non-discovery of Vulcan.

[crispycrispr]

Hi,

Why is (E) wrong? After mulling it over, I was thinking maybe because Einstein's theory actually does reject old theories and is one of the instances where negative evidence is conclusive, but I don't know. Even if that were the case, that could still be the example of the rare instance where negative evidence is conclusive?

Thank you!

[flexbubbleboi]

I thought about B, D, and E, also, but ultimately picked B (the right answer). Here was my logic -- curious if it's right, hope it's helpful.

The final sentence of A states that "Negative evidence is rarely conclusive," i.e. "The existence of a case that seems to contradict a theory is rarely conclusive."

The reason D doesn't work is because the failure to find Vulcan is a case of exactly the opposite -- where negative evidence (Vulcan's non-existence) contradicted and *helped disprove* a theory. The theorists ultimately rejected Newton's theory in favor of Einstein.

In contrast, in the case of B, the initial failure of Newton's laws' to predict Uranus's orbit is a case where there was negative evidence (the lack of the predicted orbit), but that didn't require theorists to throw out Newton's laws. Rather, there was another factor they hadn't taken into account. This situation is parallel to the situation described in the final sentence of A.

E caught my eye at first, but it's not a case of negative evidence at all. Rather, the second part of the answer (the successful prediction of Mercury's orbit) is positive evidence for the first part of the answer (Einstein's general theory of relativity).

[Adam Tyson]

The last sentence of Passage A is "But negative evidence rarely is [conclusive] either." That's what we need to see in action in passage B, crispycrispr - some example of negative evidence (evidence that a theory is incorrect because that evidence conflicts with the theory) being inconclusive (not disproving the theory). Answer E is an example of positive evidence for Einstein's theory, rather than negative evidence against Newton's.

And flexbubbleboi , your analysis is spot on! The failure to find Vulcan is negative evidence that IS treated as conclusive evidence against Newton's theory!

[pmuffley]

I just want to make sure I'm understanding this correctly...

Is negative evidence in the last line of the 1st passage referring to the idea in passage B like this:

Negative evidence is observing (initially) that there is no planet near Uranus and the positive evidence would be seeing Uranus and being puzzled???

[Robert Carroll]

pmuffley,

Negative evidence is evidence that tends to weaken a hypothesis, and positive evidence is evidence that tends to strengthen a hypothesis. The hypothesis in passage B is the hypothesis of Newton's laws of gravity and motion. Negative evidence is anything that weakens that - in the specific case of passage B, finding that the observed orbit of Uranus is not consistent with the predictions of the hypothesis. Positive evidence would, in this case, be finding something consistent with the hypothesis - once Neptune was observed, that could count as positive evidence for Newton. In this specific question, we want negative evidence that is not conclusive, because that's what the last sentence of passage A is talking about. So evidence against Newton that actually does not disprove Newton. The initial failure to predict the orbit of Uranus is negative evidence with respect to Newton, but Newton survives, so the negative evidence was not conclusive.

Robert Carroll