LSAT 155 - Section 1 - Question 18

This is a Parallel Method of Reasoning question.

The argument uses causal reasoning. Specifically, when there are multiple sufficient causes, none of them are individually necessary.

The test writers made this harder to see because the stimulus tries to obscure this reasoning whereas (A) is much more direct.

The argument opens with contextual information: a practice. To achieve the traditional hotness of Mexican cuisine or Thai cuisine, cooks are particular about using jalapeno peppers or Thai chilis.

The word "but” signals a transition to a critique of that practice. But, as experienced cooks know, if food is sufficiently spiced, it is impossible to distinguish which ingredient is causing the hot sensation.

It might have occurred to you that “traditional hotness of spicy cuisines” may not fall within the range of “sufficiently spiced” food. If it did, that’s good. Were this a Weaken or an NA question, this conceptual gap might have formed the basis of the correct answer.

But this is a Parallel Method of Reasoning question. As such, we must understand the reasoning underlying the argument. In order to do that, we must interpret this argument as a response to what cooks do. That means we charitably assume that “traditional hotness of spicy cuisines” does fall within the range of “sufficiently spiced” food because otherwise, the argument would already be irrelevant.

That’s one hurdle, recognizing that in this instance, we concede an assumption so that we can proceed with interpreting the argument. Another way to think about this is that the context constrains our interpretation of the argument.

Moving on, the premise says that once food is sufficiently spiced, then we can't tell which ingredient caused the sensation (spiciness). That means with the Mexican chef using jalapeno to cook the traditional Mexican cuisine and the Thai chef using the Thai chili pepper to cook the traditional spicy Thai cuisine, as soon as both of their dishes reach the “sufficiently spiced” threshold, we can no longer tell whether it was the jalapeno or the Thai chili that caused the spiciness.

The argument concludes that none of the hot spices traditionally used are irreplaceable. In other words, any of them could be replaced. So the Thai chef didn’t have to use Thai chili. He could have used jalapeno instead.

You might be thinking, wait, that can’t be right. Surely there must be other differences between Thai chili and jalapeno. Now you’ve encountered the second hurdle. You’re probably right about other differences in aroma or flavor, differences that have nothing to do with spiciness. And I’m sure those are the differences that explain why Thai cuisine uses Thai chili and not just any random pepper. But again, we must interpret this conclusion in context. In context, “replaceable” doesn’t mean “replaceable without any difference to the outcome.” Rather, it means “replaceable without any difference to the outcome in spiciness.” That latter interpretation greatly improves the strength of the argument. Under that latter interpretation, the conclusion follows more strongly from the premise.

But the test writers are banking on us to not take context into consideration. If we don’t, then we think this conclusion is highly problematic. And if we think that, then we’ll likely overlook Correct Answer Choice (A).

I think once we get past those two hurdles, this argument feels quite strong. More than that, the reasoning also becomes much more apparent. The reasoning is that because there are multiple causes (e.g., jalapeno, Thai chili, etc.) of a phenomenon (spiciness), then none of them is necessary to give rise to that phenomenon.

Correct Answer Choice (A) contains the same causal reasoning in a direct argument. It doesn’t give us contextual information to constrain our interpretation of the argument.

It is light-sensitive pigment in the fishes' eyes that makes it possible for them to see. That’s cause-effect. Any one of a variety of pigments makes underwater vision possible. So pigment variant A, pigment variant B, pigment variant C, any one of them makes underwater vision possible. Therefore, no particular variant is necessary for underwater vision.

The analogy is strong. Pigment variant A analogizes to Thai chili. Pigment variant B analogizes to jalapeno. Underwater vision analogizes to a certain level of spiciness. Any one of the causes can result in the effect, and therefore none of them is necessary.

One point of disanalogy is that underwater vision is binary (as presented in (A)) whereas spiciness is on a spectrum. But the argument mitigated that by treating spiciness as if it were binary by laying down a cutoff, a threshold.

Answer Choice (B) contains a circular sub-argument where the premise and the conclusion are restatements of each other.

No country that devotes the majority of its resources to the military can avoid war. Therefore, peacetime cannot persist in any nation that uses over half its resources to support its armed forces. These claims are more or less equivalent.

Answer Choice (C) says to receive a doctorate, a student must complete the required number of classes and write a dissertation. We can already move on. The reasoning in the stimulus is causal. The reasoning in (C) is conditional; it’s talking about a sufficiency-necessity relationship.

To get a PhD, you must complete the required number of classes, and you must write your dissertation. (C) continues to commit the sufficiency-necessity confusion flaw. It concludes the sufficient condition on the basis of premises that satisfy the necessary condition.

Answer Choice (D) says attending a music concert is a far richer experience than listening to a recorded piece of music. Why? Well, when playing music live, musicians depart from the original score; therefore, each live concert is a unique and irreplaceable event.

(D) implies that this “unique and irreplaceable” feature of live music is not to be found in recorded music. Well, yes. The whole point of recorded music is to be exactly the same each time you play it.

(D) assumes “unique and irreplaceable” is more valuable than its absence. On the back of that assumed value judgment, it makes its conclusion that a music concert is a “far richer experience.”

This mode of reasoning has no resemblance to the argument in the stimulus.

But on its own terms, (D) is not a strong argument precisely because of the assumed value judgment. It’s not self-evident that “unique and irreplaceable” is the “richer experience.” Reasonable people may well disagree. They may well have other values that matter more to creating a richer experience, and those other values might be better served by recorded music.

Answer Choice (E) is a cookie-cutter trap answer in Parallel Method of Reasoning questions. It talks about cooking and ingredients. The reason why this trap is here is because the test writers are thinking to themselves, “Hey, you know what? I bet if students haven't done many of these kinds of questions, they'll just see this phrase 'most similar' and they'll conflate 'most similar in reasoning' with 'most similar in subject matter.'”

Reasoning is very different from subject matter. Two arguments about very different subjects can nonetheless be very similar in reasoning, as evidenced by the argument in the stimulus and the argument in (A). And two arguments about very similar subjects can nonetheless be very different in reasoning, as evidenced by the argument in the stimulus and the argument in (E).

(E) says that good cooks always select their ingredients carefully, for they know that every delicious meal is made with high-quality ingredients. Therefore, no meal made without high-quality ingredients is delicious. Wait, that’s circular reasoning again. If every delicious meal is made with high-quality ingredients, then, of course, meals without high-quality ingredients are not delicious.