QUESTION TEXT: Selena claims to have psychic powers. So if we…
QUESTION TYPE: Sufficient Assumption
CONCLUSION: If we find out whether Selena is correct, we’ll find out if psychic powers are possible.
REASONING: Selena says she has psychic powers.
ANALYSIS: The conclusion is about what happens if we find out whether Selena is correct. Selena’s claim is either true or not true: she has psychic powers, or she doesn’t.
Note that “find out whether Selena’s claim is true” covers both finding out the claim is true and finding out that it’s false. It’s best to think about what happens in either case:
- Claim true ➞ Selena psychic ➞ psychic possible
- Claim false ➞ Selena not psychic ➞ ?????
So we have an asymmetry. If we find out Selena’s claim is true, then we do know psychic powers are possible. But if the claim is false, we can’t make a general conclusion. Someone else could be psychic even if Selena isn’t. So to solve this question we have to somehow show that if Selena is not psychic then no one is psychic.
Note that I haven’t followed a traditional diagramming structure on this question. That’s because LSAC wrote this question in such a way that a traditional diagramming structure isn’t helpful. This question is more of a decision tree.
- So? Selena still might or might not have powers. Or someone else could, even if Selena doesn’t.
- CORRECT. This covers the gap from the analysis above. Now if Selena’s claim is false we will also know psychic powers are impossible.
This answer’s contrapositive is clearer:
Selena powers➞ possible to have powers
- This is a necessary condition for the conclusion, but it doesn’t prove the conclusion correct. This is a sufficient assumption question.
- This destroys the argument! We’re trying to prove the argument correct.
- This is just a mistaken reversal of the conclusion. It doesn’t help prove the conclusion.
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