PrepTest 139

Incorrect. This answer treats what many scientists believe to be true as true, which is a jump we can't make. Additionally, this answer states that the pollution was "largely" responsible for the forest fires, whereas even if the scientists are right the stimulus only establishes that it was a factor.

Incorrect. A few issues here. First, the stimulus notes that this causal chain resulted in "unusually" large and intense forest fires. It's possible that there are usually large and intense forest fires, but the unusually strong El Nino made them even larger and more intense, making this answer wrong. Additionally, while we can negate causal statements to a certain extent, we can't do it to this extent. The reason is that we could infer that a normal El Nino should result in smaller and less intense forest fires, but that doesn't let us say that there would be "few if any"—that's a jump from a relative inference to a non-relative one.

Incorrect. We might be able to infer that these fires are larger and more intense than usual during an "unusually strong" El Nino, but this answer is about a "strong El Nino." Maybe El Nino is always strong, and it's the unusually strong ones that cause these intense forest fires.

Incorrect. This is such a tempting answer choice. It feels as if it accounts for the note that the final causal relationships are what scientists believe, validly chaining these relationships together with that caveat. However, there's a problem with this answer—it assumes that the scientists who believe air pollution causes global warming and strong El Ninos also believe the rest of the causal chain established in the premises. While these relationships are presented as fact, that doesn't mean scientists will accept them as true—that's an objective to subjective jump.

Correct. Argument or Facts:
Facts

Question Type:
Must Be True

Stimulus Summary:
An unusually strong El Nino caused a widespread drought, which caused susceptibility to fire in the tropics, which led to unusually large forest fires there in Ô97. Scientists think air pollution causes global warming, which causes a stronger El Nino.

Answer Anticipation:
This stimulus features a causal chain, which we can piece together much as we can a conditional chain. However, it's important to note that some of the causal statements are established as fact, whereas that last statement is framed as the belief of "[m]any scientists" which means that it doesn't have to be true. As such, it'll be important to split up what is true and what is believed to be true:

Scientists: Air pollution causes global warming causes stronger El Nino
Established: Strong El Nino causes drought causes susceptibility to fire causes Ô97 fires

Any answer that connects elements in this chain—and takes into account that some of the links are only believed to be true—will be correct. Additionally, there are two key differences between causal and conditional statements we need to take into account. First, we can't contrapose causal chains. Second, we can negate them, to a certain extent—removing the cause should have a negative impact on the effect.

Answer Explanation:
This answer reflects the causal chain and the final statement being qualified as a belief. It starts off by conditioning itself on the scientists' belief being true ("If air pollution was a factor in making the El Nino strong . . . "), and then chains together some of the other conditional statements. Since the unusually strong El Nino did cause those droughts, if air pollution led to that El Nino, then air pollution contributed to the drought.

Key Takeaway:
Causal statements can be chained together, similar to conditionals. Unlike conditionals, they can't be contraposed, and they can be negated to a certain extent.

If a stimulus notes that something is "believed" by a group, that doesn't establish it as true. Additionally, if something is true, it's not necessarily believed by a group. When the LSAT tries to draw an inference by combining what is established as true and what is believed by a group, there's likely a flaw in there in assuming that what the group believes is true, or what is true is believed by the group.