PrepTest 101, Section 2, Question 22
Copernicus's astronomical system is superior to Ptolemy's and(54 more words not shown)
The argument most closely conforms(7 more words not shown)
- ASimplicity should be(10 more words not shown)
- BIf one theory(27 more words not shown)
- CIf all observational(21 more words not shown)
- DOther things being(12 more words not shown)
- EOther things being(13 more words not shown)
Reading the argument
If both theories fit the observations equally well, what makes one better?
The author favors Copernicus's system even at the time it was proposed. We can't settle that comparison by importing what people discovered later. The passage explicitly says the observational evidence available then was equally consistent with both theories.
The difference the author points to is simplicity. Ptolemy has the stars moving around Earth at great speeds; Copernicus explains the apparent movement with Earth turning on its axis. The author calls that second account simpler and concludes it is superior. But simpler and better are different judgments. We need the rule that lets simplicity decide the comparison.
What we’re looking for
For the principle question, I'd predict: when the other relevant factors are equal, prefer the simpler theory. The tie in observational evidence matters. We aren't being told to ignore evidence whenever a simpler story is available; simplicity is doing the work once that evidence doesn't distinguish the two.
Working the answers
- A
This makes simplicity the only deciding factor, regardless of what else differs. But the author specifically notes that the observational evidence fits both theories equally. A would tell us to pick a simpler theory even if the evidence favored its competitor. That's a broader rule than the argument illustrates. We need the rule for this otherwise-equal comparison.
- B
The passage doesn't establish that one theory was likely true and the other likely false on the available evidence. It says that evidence was equally consistent with both. B gives a reason to prefer a likely truth over a likely falsehood, but it doesn't use the distinction the author actually relies on: simplicity.
- C
There are two changes here. “More intuitively true” means seeming true to us; the author identifies a simpler account. And “more practical to adopt” concerns usefulness in practice, while the conclusion calls one theory superior.
We shouldn't replace both parts of the author's comparison with related-sounding ideas. C has the right opening about equal observational support, but then connects different properties from the ones used in the argument.
- DCorrect
Calling the more complex theory inferior is the same comparison as calling the simpler theory superior. The wording approaches it from the other side, but the ranking is unchanged.
The “other things being equal” condition also fits the setup: the observations support both theories equally. With that condition in place, D lets the author use greater simplicity to favor Copernicus's account over Ptolemy's. It captures both the relevant difference and the limit on when that difference decides the issue.
- E
Scientific importance isn't the same as superiority. A theory might be important because of the questions it raises or the work it inspires, without being the better of two explanations. E says what simplicity means for importance; the author needs a principle connecting simplicity with which theory is better.
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