Subscription pricing
http://classic.7sage.com/lsat_explanations/lsat-64-section-1-question-22/
The following is my reasoning for why the answer to PT64S1Q22 is D, and is not B. The answer-sheet states that the answer is B, while online explanations for why the answer is B seem to me to be confusing, non sequitor, flawed, and specious. That being said, im likely wrong, and the LSAT writers and expert teachers are likely right, and I simply currently cant see why. PLEASE someone explain to me how my reasoning is flawed, and why B is correct. THANKS!!
....
Summary: The arguments conclusion incorrectly points to a cause (using the word "promoted"), based on a correlation. B indicates a correlation, not a cause, so B doesn't strengthen the argument. D, however, points to a cause (an indirect cause), helping to justify, and thus strengthen, the argument. D is therfore the correct answer.
Argument in Question Stem, presented in syllogistic format:
Sewage sludge concentrated with heavy metals = C
Surviving bacteria of C are resistant to heavy metal poisoning = Rh
Surviving bacteria of C are resistant to antibiotics = Ra
• C
• Rh
• (C --> Rh) (relationship is causal)
• Ra
☆ therfor, (C --> Ra) (relationship causal)
Flaw: The correlation of Ra, C, and (C --> Rh) does not mean there is a causation from C to Ra. The answer which strengthens this argument will show that (Rh --> Ra) (C causes Ra because it causes Rh which causes Ra) or directly that (C --> Ra) (C causes Ra) or some contrapositive to that effect (~Ra --> ~C) or (~Ra --> ~Rh)
Answer choices, presented in syllogistic format:
A) (~Ra --> ~Rh) with a correlative relationship, not causal. Also uses the word "most" further discrediting a potentially causal relationship. Wrong answer.
B) [(~C --> ~Rh) & (~C --> ~Ra)] with correlative relationships. Even if they were causal, it at most only proves the latter relationships contrapositive that (Ra --> C, relationship causal) which in no way strengthens the claim that (C --> Ra) for the existence of a causal relationship in one direction in no way indicates that such a relationship exists in the opposite direction. Wrong answer.
C) (Ra --> Rh), relationship causal. This doesn't tell us that (Rh --> Ra) for the existence of a causal relationship in one direction in no way indicates that such a relationship exists in the opposite direction. Wrong answer.
D) (C --> A), whereas the relationship is correlative and A = the presence of significant concentrations of antibiotics. This isn't the ideal answer, clearly. However, it introduces a new player (A), which in turn offers a prospective causal link. If (C --> A) then it's possible that (A --> Ra) which would obviously mean that (C --> A). Though we don't know to what degree it's possible that (A --> Ra), the existence of this new possibility is real; indeed, it makes sense from outside knowledge that higher levels of antibiotics in a medium likely means that the only bacteria who will survive are those that are resistant to antibiotics (duh). This renders the reasoning in the argument much stronger. Correct answer.
E) [(~Bs --> Rhp) & (~Bs --> Ra)] definitely wrong because it's completely changing the subject matter.
So what's my Achilles heal here?
0
4 comments
Flaw: The correlation of Ra, C, and (C --> Rh) does not mean there is a causation from C to Ra. The answer which strengthens this argument will show that (Rh --> Ra) (C causes Ra because it causes Rh which causes Ra) or directly that (C --> Ra) (C causes Ra) or some contrapositive to that effect (~Ra --> ~C) or (~Ra --> ~Rh)
First, this is correct reasoning. Although diagramming unnecessarily makes it "seem" harder. And your confusion seems to stem from incorrect application of conditional logic to causal claims.
The arguments conclusion incorrectly points to a cause (using the word "promoted"), based on a correlation. B indicates a correlation, not a cause, so B doesn't strengthen the argument. D, however, points to a cause (an indirect cause), helping to justify, and thus strengthen, the argument. D is therfore the correct answer.
B is a correlation, but it can strengthen the causal argument. The reason is because causal claims are not as absolute as conditional claims. You can see this from the discussion here (http://classic.7sage.com/discussion/#/discussion/3578/does-a-causes-b-equal-to-a-b). Notice that D is also a correlation. Tempting but wrong precisely because of the assumptions you make. Even if the answer choice explicitly links antibiotic as an alternative cause for the resistance, D does not work because heavy metal does not cause sewage sludge to have antibiotics.
Hope it helps!
How is it not flawed to say that the absence of a factor resulting in the absence of an effect indicates that the factor causes the effect? That's "standard?" I mean, I can memorize such a rule, but if I don't understand it at all I doubt it will help me. *sigh* :(
@5648
I don't know where you're getting your information from, but "D" is not correct. It's not even a close one.
B points out that, in the absence of the factor identified by the argument as the cause, there's also an absence of the effect. This is a standard way of strengthening a causal argument.