LSAT 90 – Section 2 – Question 21

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Type Tags Answer
Curve Question
PT90 S2 Q21
Weaken +Weak
+Medium 146.031 +SubsectionMedium

This is a Weaken question.

The stimulus starts with other people's position. A geologist claimed to have discovered in clay a previously unknown form of life called nanobes, which is only 1/10 the size of the smallest known bacteria. With the use of the word “however,” the author signals a transition away from context to argument. The author disagrees with the geologist. She says nanobes are probably not living things but rather inanimate artifacts of the clay’s microscopic structure. That's her conclusion. But why should we believe it? Her premises follow from the word “because.” There are two premises here. The first one is that a reproductive mechanism is a prerequisite for life. She's setting herself up to make the contrapositive argument. You already know that her conclusion is that nanobes probably are not life so you can anticipate that she will try to fail the prerequisite or the necessary condition for life. And indeed she says a nanobe is too small to contain a reproductive mechanism.

And therein lies the crucial assumption of this argument. Has she successfully failed the necessary condition? That depends on whether a nanobe being too small to contain a reproductive mechanism amounts to nanobes not having a reproductive mechanism. The argument assumes so. But if it's possible for a nanobe to be too small to contain a reproductive mechanism yet still somehow have access to or possess a reproductive mechanism anyway, then her argument falls apart.

This is what Correct Answer Choice (B) tells us. It cuts against that assumption. It says single-cell creatures can combine to form a multicelled structure and then reproduce before they disband into separate single cells again. This answer suggests that there may be a crucial distinction between a single nanobe versus a group of nanobes. The premises establish that a single nanobe is too small to contain a reproductive mechanism. But that doesn't imply a group of nanobes do not contain a reproductive mechanism, as the conclusion assumes. Even if you believe that the argument validly establishes that a single nanobe is not alive, again, that doesn't imply a group of nanobes are not alive. This is an instance where an individual member may lack a certain characteristic (a reproductive mechanism or life) yet the group may possess that characteristic.

You might object that we don't know if (B)'s description of single-cell creatures' ability to reproduce has any bearing on nanobes. As it turns out, bacteria are single-celled creatures and so we are at the right scale. But even if you didn't know that, (B) still effectively weakens the argument. This is because weakening the argument is a lower bar than proving that nanobes have a reproductive mechanism. If we wanted to prove the latter, then we would have to assume that (B) applies to nanobes, in other words, that nanobes do in fact come together to reproduce and then separate. But we are not trying to do that. We're just trying to show that the assumption the author made may be false. What was that assumption again? That an organism being too small to contain a reproductive mechanism means it has no reproductive mechanism. (B) falsifies that assumption by revealing the possibility that even if a single nanobe is too small to contain a reproductive mechanism, a group of nanobes could possess a reproductive mechanism. And that is all we need to weaken the argument.

Answer Choice (A) says no known form of bacteria is complicated enough in structure to engage in sexual reproduction. Okay, so that means all bacteria that we know of engage in asexual reproduction. Where’s the fun in that? Also, what are we supposed to do with this information? This has no bearing on the argument. We’re just trying to figure out whether nanobes failed a necessary requirement of life.

Answer Choice (C) says some scientists claim there are fossilized remains of bacteria in meteorites from Mars which are approximately the same size as nanobes. Okay, so something came from Mars and it’s about the same size as nanobes. Some scientists think that that thing is bacteria. Are they right or wrong? If they are wrong, then this is useless information. We actually don't know what the thing is. If they are right, that means it is possible for organisms from Mars as small as nanobes to reproduce. That would directly challenge the conclusion without engaging the reasoning. That’s not how we weaken arguments. Rarely, the Question Stem instructs us to directly go after a conclusion but this one says “weaken.”

Answer Choice (D) says previous definitions of life were based on research done with inferior microscopes no longer in use. That's an interesting historical fact. But are we supposed to presume that the argument above used a previous definition of life, one that was based on shitty microscopes? That seems completely arbitrary and frankly unfair to the argument.

Answer Choice (E) says animals such as cold-blooded lizards can be physiologically simpler though still larger than other animals. (E) is inviting us to analogize lizards to bacteria. It's trying to tell us that just like how bacteria are larger than nanobes, lizards are larger than other animals. And it's suggesting that even though lizards are larger, they are still physiologically simpler, and therefore even though bacteria are larger than nanobes, bacteria are physiologically simpler. That means nanobes are physiologically more complex. You don't need me to tell you how disanalogous this is. Second, even if we concede this analogy, all we can show is that nanobes are physiologically more complex than bacteria. That doesn't solve the problem of whether or not they have reproductive mechanisms. That’s what we needed to resolve.

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