#7 - Concept Reference, Weaken

[Adam Tyson]

The problem with answer choice C, lsatprep1215, is that it doesn't say that prions are NOT causing problems with the brain or central nervous system, but only that they are causing problems in other parts of the body. Those problems could be in addition to the brain and CNS issues that prions sometimes cause. This is like saying "eating fatty foods causes heart disease" and then trying to weaken that claim by saying "eating fatty foods is known to be associated with male pattern baldness and with toenail fungus, neither of which has any known connection to heart disease." Just because the pathogen has some characteristics or effects not tied to the brain does not do anything to weaken the claim that it causes brain problems!

A purported cause can have MANY effects, and adding up more effects does nothing to weaken a claim about one particular effect. We usually want our effects to have a single cause on the LSAT, but it's fine if our causes have multiple effects, so long as one effect doesn't cancel out the others.

[gingerale]

I understand why E works as the correct answer, but I don't think it necessarily undermines the claim that prions cause CJD. Perhaps CJD also has an underlying bacterial-related cause or is exacerbated by bacteria, and thus an antibacterial drug would alleviate the onset of CJD. Thus, prions could still cause CJD while the drug targets a bacterial component of CJD and alleviates onset in that manner. Should I take away from the passage that prions are assumed to be the sole and only cause of CJD?

[Jeremy Press]

Hi gingerale,

Put this one in context of the language of the passage itself. The author's claim is, "Although the discovery of the link between prions and CJD was initially received with great skepticism in the scientific community, subsequent research has supported the conclusion that prions are an entirely new class of infectious pathogens." In other words, the author believes that, in the case of CJD and potentially other diseases, prions are an infectious agent (when previously the only known ones were viruses, bacteria, fungi, and parasites). If answer choice E were true, now it's starting to look more like a bacteria is the infectious agent, and that we don't need to see prions as some new infectious agent. Is answer choice E definitively proving prions are NOT an infectious agent? No, but that's not the standard for Weaken answers. Answer choice E makes me doubt whether we need to see prions as a new infectious agent causing CJD.

Remember, too, that when the author is making a causal conclusion without qualifications (using absolute language like the language that was used in the first sentence of the last paragraph), the LSAT treats the author as assuming the cause being argued for is the sole cause. That insight, which we typically apply to causal conclusions stated in absolute terms in a Logical Reasoning stimulus, carries over to Reading Comprehension as well.

I hope this helps!

[JoshuaDEL]

The problem with answer choice C, lsatprep1215, is that it doesn't say that prions are NOT causing problems with the brain or central nervous system, but only that they are causing problems in other parts of the body. Those problems could be in addition to the brain and CNS issues that prions sometimes cause. This is like saying "eating fatty foods causes heart disease" and then trying to weaken that claim by saying "eating fatty foods is known to be associated with male pattern baldness and with toenail fungus, neither of which has any known connection to heart disease." Just because the pathogen has some characteristics or effects not tied to the brain does not do anything to weaken the claim that it causes brain problems!

A purported cause can have MANY effects, and adding up more effects does nothing to weaken a claim about one particular effect. We usually want our effects to have a single cause on the LSAT, but it's fine if our causes have multiple effects, so long as one effect doesn't cancel out the others.

Hello, I'm still confused as to why C is not the answer while E is. C does in fact say that prions are NOT affecting the brain and the passage clearly suggests that CJD is caused by degenerative conditions in the brain, not anywhere else. So if the prions were later found to not cause the degenerative conditions in the brain or the CNS, then to me, that clearly undermines the claim that prions cause CJD. To your example, I would probably think C is more like "eating fatty foods is known to be associated with male pattern baldness and with toenail fungus, NOT affecting the heart." I agree that not having a connection to the heart as worded in your example does not affect the argument. But the choice is suggesting that it is NOT causing problems in the brain rather than saying that the degenerative condition has no connection to the brain or CNS. If the passage suggested that CJD could be caused by degenerative conditions in other areas of the body, then I would understand C being a wrong choice. I'm not sure how C and the claim that prions cause CJD could coexist.

Regarding choice E, it is only suggesting an alternate cause. If the question said, "Which one of the following, if true, would most undermine the claim that ONLY prions cause CJD?", then I would 100% agree with E being the answer. But it could well be that both prions and bacteria could cause CJD. It doesn't undermine anything about whether prions do or do not cause CJD but rather whether ONLY prions cause CJD or not.

Thanks in advance

[Rachael Wilkenfeld]

First, remember that if you find an alternate cause, you weakened the argument. So for answer choice (E), Joshua, we can see the alternate cause (bacteria) as weakening the suggested cause (prions).

For answer choice (C), it's important to note that the answer choice is talking about prions impacting something outside of the brain and something that is not CJD. Based on the information in the passage, I wouldn't be surprised by that. The description of prions given by the article is that they are proteins naturally occurring in the body that are shaped in an incorrect way. It would be expected that those wouldn't just pop up in one body part/area, and could potentially pop up anywhere. And wherever they are, misshapen proteins could muck up body systems. There's nothing special about the brain/CNS and prions discussed in the passage. It's just that prions THERE seem to be the cause for CJD.

Answer choice (C) is talking about something not really relevant to our conclusion. It doesn't impact the causal relationship between prions in the brain and CJD to discuss prions somewhere else causing something else. It would be like if I said a bacteria in the nose causes sinus infections. It wouldn't weaken that to say that a bacteria in the lungs causes pneumonia. Two totally different situations.

Hope that helps!

[Henry Z]

I read the explanations above and I got the point why (C) doesn’t deliver—in the real world logic. However, I chose (C) over (E) because I followed the LSAT logic. As in LR, it’s a valid way to attack the causal argument by showing the cause (prion) occurs without the effect (CJD/affecting the brain or the central nervous system). (C) does exactly that.

Furthermore, I feel (E) at best suggests there’s a negative correlation between bacteria and CJD, but It doesn’t attack the causality. What if prion is only a partial case? What if both prion and bacteria can cause CJD?

So my question is: should we bring LR’s Causal Assumption into RC, and use the classic ways to attack as if it’s a LR Weaken Q?

[Robert Carroll]

Henry Z,

LSAT logic is real world logic. Note that what you're describing answer choice (C) as doing is not actually what it's doing. Prions' ability to cause CJD does not at all preclude their ability to cause other conditions as well. Further, nothing in answer choice (C) says that the subjects don't have CJD also! The subjects have degenerative conditions not affecting the brain or central nervous system. Do they also have CJD? They might - it's not mentioned, so we can't make any assumptions.

To illustrate why answer choice (C) does nothing, consider the true fact that bacteria can cause meningitis. If I found that bacteria could also cause a skin infection in a person's foot...that wouldn't mean the bacteria aren't really causing meningitis! Bacteria can cause multiple things. Causing one thing does not make it less likely it can also cause something else - causation is not a limited resource such that things that have some effects have less ability to also have other effects in other cases.

If you're right that answer choice (E) suggests a negative correlation, then that precisely does attack causality. Correlation is evidence of causation. A correlation in the opposite direction will be evidence against causation. Don't misunderstand me as saying that correlation proves causation - I'm saying no such thing. But correlation is always SOME evidence of causation, and a negative correlation or lack of correlation will therefore be evidence against causation. So, from your perspective, answer choice (E) weakens the argument.

The author's position is that prions are THE cause of CJD - the author talks about "the pathogen responsible for CJD", for instance. So discussions of partial causes seem irrelevant here.

RC Weaken questions with causal reasoning are dealt with the same way as LR Weaken questions with causal reasoning, yes.

Let me know if I can help with anything else!

Robert Carroll

[jimmy1115]

Hi,

just want to clarify my understanding of causal relations using this q as an example. So the relations: prions caused CJD.
to undermine it, we either show that the cause if present while the effect is not or vice versa.

Answer C is incorrect because it only shows that the cause (prions) can have some other effects, but does not show that the effect (CJD) is not present (we don't know).
Had it shown that prions are present while CJD is not, then this would effectively weaken the author's argument right? Because the author assumes that the cause always produce the effect.

Answer E is correct because it implies that other things (bacteria) are causing CJD, so in this case, cause (prions) are allowed to be absent, while effect (CJD) is present. This undermines the presumption that the author makes (in absolute causation): the stated cause (prions) is the only cause of the effect (CJD) by introducing a possible alternative cause (bacteria).

Am I understanding this (question and causal logic) correctly and comprehensively?

thank you

[Chandler H]

Hi Jimmy,

Good question! With regards to answer choice (C), you're right to say that it only shows that the cause can have other effects, which is not the same as saying that the effect (CJD) is not present. However, be careful! In this case, the cause (prions) does NOT necessarily always produce the effect (CJD). We are NOT told in the text that the presence of prions in the body always leads to CJD. In lines 25-30, we are told the following:

(25) Upon further study, scientists discovered that
prions normally exist as harmless cellular proteins in
many of the body’s tissues, including white blood cells
and nerve cells in the brain; however, they possess the
capability of converting their structures into a
(30) dangerous abnormal shape.

So the presence of prions does not always lead to CJD.

Your understanding of why answer choice (E) is correct is all good! You're completely right that it introduces a possible alternative cause. Hope this helps clarify things!

[jimmy1115]

Hi Chandler,

thank you for your reply, so the line 'they possess the capability' indicates that they 'can' but do not have to always produce CJD right.

So under this non-absolute casual relations, would the line 'study shows that prions is present while CJD is NOT' weaken the author's argument?

As I am going through the advanced causal reasoning section in the bible, it says that when the causal relation is less than absolute, presenting cause present, effect absent' or 'cause absent, effect present' (which is what answer choice E is doing) will not effectively weaken the relations. If this is true, how do we better understand the logic behind (E) can effectively weaken a causal relation that is less than absolute by presenting a possible alternative cause? Is it simply because it is the best choice out of all? i.e. while it does not absolutely destroy the reasoning, it still has a weakening force.

thank you