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The stimulus for these two questions is in the Power Score LRB's "Premise and Conclusion Analysis Drill", in which you are supposed to evaluate the strength or weakness of a given stimulus's argument. According to PS, this argument is "strong", but I do not see how this is the case. Here's a rundown of the argument:

P1: Many species adapt to their environment, but it is commonly believed that only the most highly evolved species alter their environment in ways that aid their survival.

Conclusion: This characteristic (altering for survival) is quite common.

P2: Certain species of plankton generate a gas that turns into sulfate particles in the atmosphere.

P3: The sulfate particles result in water vapor condensation, which forms clouds.

P4: In addition, it is true that the formation of clouds over the ocean is largely dependent on the presence of these particles.

P5: More clouds means more sun is reflected, which in turn means the Earth absorbs less heat

Sub-Conclusion/P6: Thus, Plankton cause the earth to be cooler, which is beneficial to the Plankton.

The argument is strong inasmuch as it establishes that some non-highly evolved species alter their environment to aid their survival, but aside from that, it's not strong. According to PS, though, it implies strong support for the notion that aiding for survival is "quite common", because on the basis of what the argument establishes it is "...likely that other species exhibit this characteristic". I grant that it's fair game to assume that plankton exhibiting the characteristic slightly increases the probability that other non-highly evolved species do as well, but to say that it is "likely" is to infer too much, or at the very least (if it is actually true in the real world) to incorporate specialized knowledge that is not fair game for the LSAT. Furthermore, and more importantly, that it is "likely that other species exhibit this characteristic" does not imply that it is likely that is "quite common", it just adds increases the probability of it being so very slightly. Right? Or what am I missing? Sorry for the long-ish post.

Is it just me or are you just overthinking the LSAT?

The two questions ask for the conclusion and how the argument is furthered. No need to look too deeply into it.

I see where you're coming from, but I don't think I'm over-thinking anything. Argument evaluation is crucial for the LR section.

I think their use of the term "common" doesn't mean what you are thinking, which is that the characteristic is seen very often. I think what they mean by using the word "common" is that it isn't as limiting to highly evolved species as one might think.


I mean, how do you expect them to prove that the characteristic is quite common? List every single species that has that characteristic? Even if they did list, for example, 100 species that had the characteristic...that doesn't mean the argument can't be weakened. You could easily say, "Well there are a million species and so 100 out of a million means that the characteristic IS actually uncommon."

ws81086n wrote:I see where you're coming from, but I don't think I'm over-thinking anything. Argument evaluation is crucial for the LR section.

Here's the deal: I've only got 35 minutes to get through the LR. I'm going to read the question before the setup, so I know what I'm looking for. If the question is "Which of these statements is most strongly supported by the above?" then I'm not going to waste time looking for a flaw in the argument. The same applies here. If you already read the questions, you'd know to be looking for a main point and the argumentative strategy. It isn't worth your time to evaluate the strength of the argument, because for the sake of the LSAT the argument is both true and strong.