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# PT91.S2.Q21 - Invisible light-absorbing medium

Alum Member
edited September 2021 27 karma

Struggling with this one. The negation of E wrecks the argument and is what I picked, but I am having a really difficult time eliminating A. Any thoughts on how to justify getting rid of it? Thanks!

Admin Note: Edited title. Please use the format: "PT#.S#.Q# - brief description of the question"

• Alum Member
edited September 2021 128 karma

Hey! I can see if I can help since I just took 91! (A) sounds more like a Sufficient Assumption, that's probably why you're inclined to it. (E) is more necessary compared to (A). The premise of the conclusion is "low visibility in question is already completely explained by the general theory of relativity," that's why there is no reason to believe the hypothesis is correct. Not for any other reason, at least in this stimulus. But if you put (A) into the reasoning, then it doesn't have to be the hypothesis is wrong because we already have general theory of relativity, it could be something else, maybe has nothing to do with the general theory of relativity. That's why (E) is more necessary to this argument than (A) is.

I like to think of it this way: We're trying to guard the whole argument of the reasoning, so the premise must follow the conclusion perfectly. So even if the conclusion can be the same for another reason, at least in this stimulus, it must follow from this premise they provided for you!

• Alum Member
82 karma

A states that the invisible light spectrum would not adequately explain the phenomenon.
Conclusion: there is no reason to believe this to be the case
premise: Einstein's relativity COMPLETELY explains this phenomenon

Let's negate A. We get invisible light spectrum would adequately explain the phenomenon. That is not necessary on the ground that it can explain the thing adequately, but Einstein's relativity just does it much better by COMPLETELY explaining it. This doesn't kill the argument. We can still say that yea this kinda explains it, but Einstein's theory explains it the best, so we don't need to consider this theory.

I have some examples from my time doing reading comp on lsat. Let's say the geocentric theory did a pretty good job in explaining the movement of the stars and the observations of seasons, day/night or whatever I got this from lsat. Then we got Copernicus heliocentric theory. It explains the phenomenon so much better comparing to geocentrism. People back then can say that hey, if heliocentrism explains this so perfectly, why do we still need to consider geocentrism? "But geocentrism can explain it adequately tho come on guys," said a geocentrist. See how little that does to rekt the argument? We still don't need to consider geocentrism if heliocentrism does a great job already.

Negating AC E would kill the argument, as you already know. Hope this helps