Many people do not understand themselves, nor do they try to gain self-understanding. These people might try to understand others, but these attempts are sure to fail, because without self-understanding it is impossible to understand others. It is clear from this that anyone who lacks self-understanding will be incapable of understanding others.
The reasoning in the argument is flawed because the argument
(A) mistakes something that is necessary to bring about a situation for something that in itself is enough to bring about that situation
Keep for now. We'll come back to this. Ok. Let's break this down
something that is necessary to bring about a situation for something that in itself is enough to bring about that situation. A is required for B to occur. B is not enough by itself for B to occur. Does mistaking this logic clarify what is wrong with the argument? I don't think so. The idea that you can understand someone else without understanding yourself is a valid critique, but it doesn't attack the logic of the argument. Frankly, this answer choice could trip up many people. It took me while to understand it and had I done so on an exam it might not have been worth it.
(B) fails to take into account the possibility that not everyone wants to gain a thorough understanding of himself or herself
The question is asking why the argument is flawed. This added information is irrelevant. Whether this is true or not doesn't explain why the argument's logic is flawed. At least some people, according to this statement, want to gain a thorough understanding of themselves, right?
(C) blames people for something for which they cannot legitimately be held responsible
A freebie elimination, I daresay. This doesn't affect the argument's legitimacy in anyway. The argument doesn't blame people for being able to self-understand or not anyway.
(D) makes use of the inherently vague term “self-understanding” without defining that term
This is a critique you might want to mention were this AWA, but it does not specifically relate to the argument's logic.
(E) draws a conclusion that simply restates a claim given in support of that conclusion
The argument pretty much states that if you cannot self-understand, you cannot understand others. Therefore you cannot understand others, if you cannot self-understand. This convenient 'evidence cycle' is (E)
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