LSAT 6 | Section 3 | Logical Reasoning: Q23

LR Question 23 Explanation

QUESTION TEXT: Anthony: It has been established that over 80 percent…

QUESTION TYPE: Method of Reasoning

CONCLUSION: It is absurd to say that marijuana leads to heroin use based solely on the fact that 80% of heroin users had a past history of marijuana use.

REASONING: 100% of heroin users have a history of drinking water.

ANALYSIS: Judith uses one of my favorite argumentative strategies: the reducto ad absurdum. Judith uses the exact same (flawed) reasoning as Anthony, but her example shows how silly it is. Obviously water use doesn’t lead to heroin.

Anthony has proven there is a correlation between marijuana and cocaine, but he hasn’t proven marijuana causes cocaine use.

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1. Judith did not disagree with Anthony’s statistics. She just said it was absurd to cite those statistics.
2. I almost picked this because I saw the word absurd. But Judith isn’t saying Anthony’s conclusion leads to absurd consequences. She even says it may be correct. Her claim is that Anthony’s entire argument is absurd and produces false results if we use the same reasoning with different terms.
3. Anthony didn’t claim that marijuana is unsafe. He only said it leads to heroin. And Judith didn’t discuss anything we know for sure leads to heroin.
4. CORRECT. Yes. It’s clearly false that water use leads to heroin. Everyone drinks water and most people don’t use heroin. Yet Judith used exactly the same reasoning as Anthony. Therefore Anthony’s reasoning is clearly bad.
5. Judith’s argument is strictly limited to saying that Anthony’s argument is wrong. She might believe statistics could prove things in other circumstances.

Recap: The question begins with “Anthony: It has been established that over 80 percent”. It is a Method of Reasoning question. Learn how to master LSAT Method of Reasoning questions on the LSAT Logical Reasoning question types page.