LSAT 158 | Section 3 | Logical Reasoning: Q21

LR Question 21 Explanation

QUESTION TEXT: Professor: Many scientists hypothesize that there is…

QUESTION TYPE: Necessary Assumption

CONCLUSION: There is no reason to believe that the scientists’ “light-absorbing medium” hypothesis is correct.

REASONING: The scientists say that the medium would explain the low visibility of other systems from Earth. But general relativity already explains the low visibility.

ANALYSIS: The professor disputes that the hypothesis is necessary to explain the low visibility of other systems. They claim that relativity already fully explains that problem. But does that actually leave “no reason” to believe it is correct?

The correct answer, when negated, will wreck the argument. Here, we’ll use the negation test to find which answer is necessary.

___________

1. The negation of this answer doesn’t break the argument. The author isn’t saying the hypothesis doesn’t explain it, but that it’s already explained.
   Negation: The low visibility of other systems is adequately explained by the “light-absorbing medium” hypothesis.
2. Similar to answer A – the argument is not saying the hypothesis doesn’t explain the low visibility. The point is that it is unnecessary.
   Negation: The “light-absorbing medium” hypothesis can be correct even if it does not adequately explain the low visibility.
3. This doesn’t matter – we don’t care what makes a hypothesis likely to be correct. Likely is a weak word, and the professor is arguing the opposite.
   Negation: A hypothesis is not likely to be correct if it adequately accounts for a phenomenon that isn’t already accounted for by an existed theory.
4. This is irrelevant – it doesn’t matter to the argument if they accept it or not.
   Negation: Most scientists positing the hypothesis don’t accept the general theory of relativity.
5. CORRECT. When we negate this, it ruins the argument. The author is relying on the theory of relativity being distinct from the “light-absorbing medium” hypothesis.
   Negation: The general theory of relativity depends on the “light-absorbing medium” hypothesis.

Recap: The question begins with “Professor: Many scientists hypothesize that there is”. It is a Necessary Assumption question. Learn how to master LSAT Necessary questions on the LSAT Logical Reasoning question types page.