How to Weaken an Argument

You do not need to find an answer that destroys the author’s position. Instead,
simply find an answer that hurts the argument.
The one time you might see an answer choice attack a premise is when that
“premise” is a sub-conclusion. That is, when a conclusion of one premise is used
as a premise to support another conclusion.
The key to weakening an LSAT argument is to attack the conclusion. But, keep
in mind that to attack is not the same as to destroy. Although an answer that
destroys the conclusion would be correct, this rarely occurs because of the
minimal space allotted to answer choices. Instead, you are more likely to
encounter an answer that hurts the argument but does not ultimately destroy the
author’s position. When evaluating an answer, ask yourself, “Would this answer
choice make the author reconsider his or her position or force the author to
respond?” If so, you have the correct answer.
Because arguments are made up of premises and conclusions, you can safely
assume that these are the parts you must attack in order to weaken an argument.
Let us discuss each part, and the likelihood that each would be attacked by an
answer choice.
1. The Premises
One of the classic ways to attack an argument is to attack the
premises on which the conclusion rests. Regrettably, this form of
attack is rarely used on the LSAT because when a premise is
attacked, the answer choice is easy to spot. Literally, the answer will
contradict one of the premises, and most students are capable of
reading an argument and then identifying an answer that simply
negates a premise.
In practice, almost all correct LSAT Weaken question answers leave
the premises untouched.
2. The Conclusion

The conclusion is the part of the argument that is most likely to be
attacked, but the correct answer choice will not simply contradict the
conclusion. Instead, the correct answer will undermine the conclusion
by showing that the conclusion fails to account for some element or
possibility. In this sense, the correct answer often shows that the
conclusion does not necessarily follow from the premises even if the
premises are true. Consider the following example:
All my neighbors own blue cars. Therefore I own a blue car.
Even though the statement that the neighbors have blue cars is
entirely reasonable, the weakness in the argument is that this fact has
no impact on the color of the car I own. In this overly simplified
problem, the correct weakening answer would be something along
the lines of, “The cars of one’s neighbors have no determinative
effect on the car any individual owns.” Would that conclusively disprove
that I own a blue car? No. Does it show that perhaps I do
not own a blue car? Yes. Does it disprove that my neighbors own
blue cars? No.
Answers that weaken the argument’s conclusion will attack
assumptions made by the author. In the example above, the author
assumes that the neighbors’ ownership of blue cars has an impact on
the color of the car that he owns. If this assumption was shown to be
questionable, the argument would be undermined.
The stimuli for weaken questions contain errors of assumption. This
makes sense, because the easiest argument to weaken is one that
already has a flaw. Typically, the author will fail to consider other
possibilities or leave out a key piece of information. In this sense the
author assumes that these elements do not exist when he or she
makes the conclusion, and if you see a gap or hole in the argument
immediately consider that the correct answer might attack this hole.
As you consider possible answers, always look for the one that
attacks the way the author arrived at the conclusion. Do not worry
about the premises and instead focus on the effect the answer has on
the conclusion.
Personalizing helps you see the argument from a very involved perspective, and
that helps you assess the strength of each answer.
So, we know that we must first focus on the conclusion and how the author
arrived at the conclusion. The second key to weakening arguments is to
personalize the argument. Most students perform considerably better when they
see the argument from their perspective as opposed to trying to understand the
issues abstractly. When analyzing the author’s argument, imagine how you
would respond if you were talking directly to the author. Would you use answer
choice (A) or would you prefer answer choice (B)? Students who personalize
the argument often properly dismiss answer choices that they would have
otherwise wasted time considering.