LSAT 15 - Section 2 - Question 16

This is a Necessary Assumption question. We know because the question stem is asking for an assumption the argument depends on.

The amaryllis plant goes dormant when its soil dries up. That seems like a handy trick and is probably an important adaptation. So, what about it? Oh. It looks like we’re jumping straight into a conclusion. If we’re keeping these as house plants and want them to really thrive, we should withhold water to mimic its natural habitat by creating a dry season for it. Well, I create dry seasons for my house plants sometimes, but they don’t particularly thrive from it. It might actually be nice to have a plant that has an evolutionary adaptation to negligent house plant owners.

This is a really common argument type. It’s the simplest argument structure there is: Premise, therefore, conclusion. A therefore B. It is never valid because there is absolutely nothing which links the premise to the conclusion. The premise and conclusion can be intuitively related, and these arguments can sometimes even seem reasonable on the surface. But a formal analysis shows us what a disaster this sort of argument always is. You can’t say “A therefore B” without establishing any relationship between A and B. Our answer will almost certainly be something that establishes some connection between our premise and conclusion.

So our premise is about the amaryllis’s natural habitat and our conclusion is about what we should do for our house plant amaryllis to thrive. We need something which links the plant’s well-being to its conditions in its natural habitat.

Answer Choice (A) No. We could not care less about what other plants do. The argument in the stimulus does not stray from the amaryllis.

Answer Choice (B) Well, first of all, this doesn’t sound true at all. Something that can handle a bit of drought sounds like an ideal house plant to me. But that doesn’t matter. It doesn’t have to be true. We don’t know if these plants are hard or easy to care for and we don’t care. Whether they’re harder or easier to keep than other plants has no bearing on our job in helping them thrive.

Answer Choice (C) No, though I can see why this might be attractive. If we’re trying to mimic its natural habitat, wouldn’t this be best? Well, yes. But are we trying to mimic its natural habitat? Not necessarily. We are trying to create conditions in which it will thrive. This answer requires the further assumption that its natural habitat is optimal for it to thrive. We do not know this. Life may find a way, but that doesn’t mean it’s thriving.

Answer Choice (D) Tricky. If it doesn’t thrive then it probably wasn’t dormant long enough. No, this doesn’t need to be true. There could be many other conditions required for this thing to do well, any one of which may explain why a plant might be struggling. Maybe it got too little or too much sun. We just don’t know. This does create some relationship between the premise and the conclusion, though, so it might be tempting.

Correct Answer Choice (E) This looks good, though the test writers do make some effort to disguise it since they never explicitly talk about thriving. But it’s there. It establishes that the plant’s dormancy benefits it beyond merely preventing it from dying. If its dormancy period only prevents death and there is no further benefit, then there is no reason to intentionally subject it to drought conditions. There’s a lot of room between not-dying and thriving. This answer provides us with something more than simply not dying. There is some benefit to dormancy other than just not dying. Now, we may help it thrive by withholding water because we are providing whatever this benefit might be. If this is not true, however, then drought provides no benefit whatsoever and, thus, cannot help us to thrive.