Logical ReasoningDifficulty: Hard

PT139 S4 Q20 Explanation

Unusually large and intense

A free, expert breakdown of this official LSAT Logical Reasoning question.

TopicsMust be True

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Stimulus

Unusually large and intense forest fires swept the tropics in 1997. The tropics were quite susceptible to fire at that time because of the widespread drought caused by an unusually strong El Niño, an occasional global weather phenomenon. Many scientists believe the by the global warming caused by air pollution.

What this question is testing

Must be True

Your task

Break the argument into its conclusion and evidence, then do exactly what the question stem asks with that structure.

Common trap

Answers that sound relevant to the topic but don't connect to the argument's actual reasoning.

Winning move

Predict what a right answer must do, then test each choice against the conclusion-evidence gap.

Reading along? Open the full official question in LawHub — we show a fragment here and keep the reasoning in our own words.

The question
20.

Which one of the following can be properly inferred from the

Answer choices

  1. Trap7% picked this

    Air pollution was largely responsible for the size and intensity of the forest fires that swept

    Opinion vs. Fact Too Strong = largely responsible I hate this answer, and in many universes in the multiverse I'm probably picking it. It rewards us for having assembled the grand causal chain of Air Poll. → Glob Warm → Big Niño → Drought → Fire risk ↑ However, we're only told that "many scientists believe" that air pollution led to global warming which led to the weirdly big El Niño. This answer treats that as a fact and also amps up the burden of proof by saying that air pollution was largely responsible, when the safe inference would be somewhat responsible.

  2. Too Strong: few if any4% picked this

    If the El Niño in 1997 had not been unusually strong, few if any large and intense forest fires would have swept

    On Most Supported tasks, we are allowed to flip a Causal Difference-Maker and say "If it hadn't happened, we wouldn't have seen (as much) of the Effect". (This is a Must Be True task, though) We know that a weirdly strong El Niño led to a big draught, which made forests more susceptible to fire. So, on Most Supported, we can say "if there hadn't been a weirdly strong El Niño, the forests would have been less susceptible to fire." But this goes too far in predicting "few, if any" large fires. We just know less susceptible, not barely susceptible at all.

  3. Too Strong: generally10% picked this

    Forest fires in the tropics are generally larger and more intense than usual during a

    Although we have some support for the idea that strong El Niño's lead to more drought and thus susceptibility to fire, we can't derive a Must Be True inference that in 51% or more of strong El Niño ears there have been larger and more intense tropical forest fires. The causal information is presented as "susceptible to fire at that time because of drought and El Niño".

  4. Out of Scope34% picked this

    At least some scientists believe that air pollution was responsible for the size and intensity of the forest fires that

    Out of Scope: scientists beliefs about fires There's a recurring flaw LSAT sometimes goes back to in which we assume that someone believes an implication of one of their beliefs. For example: 2 is a prime number. Tania believes that her brother Ricky's age is 2, so Tania believes that her brother Ricky's age is a prime number. That's flawed since Tania might not even know what a prime number is. We have no way of inferring her other beliefs. We can't assume that she knows all relevant information or is capable of or inclined to make rational connections between her beliefs. (Like even if I know that alcohol is bad for my body and know that scotch is alcohol, I might not believe that scotch is bad for my body.) Similarly, these scientists who believe that El Niño was exacerbated by global warming that was caused by pollution don't necessarily know that El Niño spurned a big drought which amped up the risk of fires. So this answer is congratulating us for having seen the big causal chain, but they're using it against us. What some/many scientists believe only goes the first couple links in the chain. Air Pollution → Global Warm → Big Niño → Drought → Fire risk ↑ [ many scientists believe ]

  5. Correct45% picked this

    If air pollution enhanced the strength of the El Niño in 1997, then it also contributed to the

    Why this is right

    This doesn't quite reward us for having seen the grand causal chain, but it acknowledges that we don't know the first two connections yet. Air Pollution → Global Warm → Big Niño → Drought → Fire risk ↑ [ many scientists believe ] Since we know the last three ideas, Big Niño → Drought → Fire risk ↑ we could write an answer with any hypothetical that leads to the Big Niño, and that causal precedent would lead to Drought and Increased Susceptibility to Fire. For example, this would also be a correct answer (A) If Debra's ocean farts enhanced the strength of the 1997 Niño, then they also contributed to the widespread drought that year.

    Skill tested: Must be True · how this choice captures the argument's function is the move to repeat next time.

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