Logical Reasoning

PT152 · S2 · Q18 Doctor: Angiotensinogen is a protein

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Doctor: Angiotensinogen is a protein in human blood.

Conclusion

Disease X must be a cause of high blood pressure.

Evidence

Disease X usually causes angiotensinogen levels to go up.

Typically, the higher a person's angiotensinogen levels, the higher that person's blood pressure

Evaluation

The author's causal story is that: Disease X → Higher → Higher blood angiotensinogen pressure levels levels

She has established that Disease X causes higher angiotensinogen levels, but she hasn't established that higher angiotensinogen levels cause higher blood pressure.

We know that the two things are tightly correlated (typically rising and falling together), but it's possible that higher blood pressure causes higher angiotensinogen levels, or that both higher blood pressure and higher angiotensinogen levels are caused by some underlying third factor.

Goal

Look for an answer calling out the author's move from "higher angiotensinogen is correlated with higher blood pressure" to "higher angiotensinogen causes higher blood pressure".

Or look for an answer posing the alternate interpretations, that maybe "higher blood pressure causes higher angiotensinogen " or maybe .

18.

The doctor's argument is most vulnerable to criticism on which one of the following grounds?

  1. It confuses a necessary condition

    No Conditional Logic

    In order to commit the famous Necessary vs. Sufficient flaw, there needs to be some conditional logic. Our two premises (typically and usually) are not conditional.

    7% picked this

  2. It overlooks the possibility that

    Bad Conclusion Match

    The syntax of "fails to consider that even if X, it may not be Y" implies that the first idea should match the Premise and the second idea should match the opposite of the conclusion. "Even if your Premise is true, your Conclusion may still be wrong" is basically our objection to every argument. So does the premise have a condition that causally contributes to a given effect? Yes, Disease X usually causally contributes to higher angiotensinogen levels. Okay, so the 2nd half is saying "other factors may fully counteract the higher angiotensinogen levels in the presence of Disease X". This is an objection saying, "Even if Disease X wants to cause your angiotensinogen levels to go up, something else in that situation would be fully counteracting that and keeping your angiotensinogen levels from going up". That doesn't sound like any sort of objection to this argument. We want to object, "even if Disease X causes your angiotensinogen levels to go up, your blood pressure might not go up".

    10% picked this

  3. Correct

    It illicitly infers, solely on

    Why this is right

    Does the author conclude/assume that one phenomenon causally contributes to another? Yes, the conclusion is that Disease X increases blood pressure. The assumption is that higher angiotensinogen levels increase blood pressure. Does the evidence say that Disease X and blood pressure, or that higher angiotensinogen and higher blood pressure, are correlated? Yes, we have a premise that says typically angiotensinogen and blood pressure go hand in hand. This answer is annoyingly using "infer" to refer to something the author assumed, not something the author concluded explicitly. That does happen in some other correct Flaw answer choices. What makes this doubly annoying though is that there is also a causal conclusion, and the causal conclusion is based on two pieces of evidence (Disease X causes higher angiotensinogen + the correlation between angiotensinogen / blood pressure). Meanwhile, this answer is saying that an inference is built solely on a correlation. This answer choice wouldn't apply to the author's argument as a whole. So we have to understand this answer as testing a subsidiary argument happening within the author's broader argument: "the author concluded from the correlation between angiotensinogen and blood pressure, that higher angiotensinogen causes higher blood pressure"

    Skill tested: Flaw · how this choice captures the argument's function is the move to repeat next time.

    71% picked this

  4. It confuses one phenomenon’s causing

    Never Correct

    A flaw answer that says "the author thinks X caused Y, but in reality Y caused X" has never been right (as far I know). That's because we can't be sure that Y caused X. It's just a possibility. Our answer choice should be saying, "His argument is flawed because it overconfidently arrives at one possible explanation for the data, when other possibilities exist". It's fine to say "the author thinks X caused Y, but Y may have caused X". But it's not fine for us to be sure that reverse causality is happening. This answer would have to say something more tentative, like "It interprets one phenomenon's causing a second from evidence consistent with the possibility that the second phenomenon causes the first".

    7% picked this

  5. It takes for granted that

    Bad Evidence Match

    An answer with the syntax "It takes for granted that if X and Y, then Z", is saying, "The author goes from knowing X and Y in the evidence, to concluding Z." In the evidence do we have one phenomenon that often causes a second? Yes, Disease X often causes higher angiotensinogen levels. Do the evidence also say that "higher angiotensinogen levels cause some third phenomenon"? No, the evidence says that "higher angiotensinogen levels are correlated with some third phenomenon (higher blood pressure)". From this mismatch, we could stop reading and eliminate. The last part of the answer would be saying that the conclusion is that "Disease X can never be the immediate cause of higher blood pressure", and that would also be a bad match for our conclusion.

    4% picked this

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