QUESTION TYPE: Necessary Assumption
CONCLUSION: We won’t develop certain important medicines unless we protect tropical rain forests.
REASONING: Some medicine has been made from substances found only in tropical rain forests. There are lots of plant species scientists haven’t looked at, and some of them probably have medically important substances.
ANALYSIS: This sounds like a pretty good argument. But the author ignores a possibility: maybe the substances in the unexamined plants are the same medically valuable substances we’ve already found in other plants.
- CORRECT. If this isn’t true the argument fails.
Negation: There are no new medically useful substances in the plants we haven’t studied. The substances are the same as those already found in other plants.
- If this is true it weakens the argument. The author emphasized that some important plants only grow in the tropics.
- This seems tempting, because it strengthens the argument. But an answer isn’t right just because it strengthens the argument. The answer has to be necessary. “Most” statements are almost never necessary, because the negation moves us from 51% to 50% (i.e. “not most”). An insignificant change in almost all cases.
Negation: Only 50% of plants studied had medically important substances.
- This doesn’t have to be true. This answer would be right if it had said “At least some substances of medical value will eventually be discovered if scientists study the unexamined plants.”
It isn’t necessary that scientists discover all the substances. We only need to know that they would discover some of the substances.
- This answer talks about what we should do. The stimulus was only about what is true. On the LSAT, there is zero overlap between what should be true and what is true. So this answer is talking about the wrong thing.
This answer feels like it’s true but that’s not what we’re looking for. We’re looking for a necessary assumption.
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