Underlying Philosophy/Theory on Weaken An Arg. LR Questions Forum

[jwinaz]

I'm having some trouble seeing the underlying theory or philosophy behind logical reasoning questions that involve weakening an argument.

For example, in the OCT 2011 LSAT, SECT 3, # 15. There's an argument given from some newspaper columnist and we're asked what would weaken that argument (if it were true)?

I feel like I don't even know where to begin on these weaken problems.

Are there any expert LSAT masters out there who can offer their expert opinion?

[CardozoLaw09]

I'm no LSAT master but for weaken questions your aim should be primarily to attack the conclusion and/or the reasoning that led the stimulus to make that conclusion. Correct answers for weaken questions tend to pick up on assumptions that the author of the stim made in his/her argument; the answer will make that assumption explicit. So for the question you're referring to, the columnist has made the assumption that their city is comparable to the other cities' economies in that the economic adviser hired will help replicate the effects experienced by the other "larger" economies. Because the city councilor's economy is smaller than that of the other regions', the impact the adviser will have might not be the same. This weakens the conclusion that the city council hiring the economic adviser will likely lead to a big payoff in the long run. Hope this helps

[toothbrush]

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[bp shinners]

For any Operation family question (Strengthen, Weaken, Sufficient, Necessary, Crux), the argument will be flawed. This is because you can't strengthen a valid argument (you're already at 100% valid), and you can't weaken it without attacking a premise (which you can't do on the LSAT).

So the first step is to find the conclusion, then the relevant premises. Then, find the flaw in the argument.

In a strengthen/weaken question, there are different strategies based on the flaw. If it's a causal fallacy, there's one method; if there's any other fallacy, it's another. Let's look at the strategies for a weaken question.

If the flaw is a causal argument, pull out the purported cause and effect. Then, find an answer that does one of these three things:
1) Gives you an example where you have the same cause, but a different/no effect.
2) Gives you an example where you have no cause, but get the effect.
3) Identifies an alternate cause for the purported effect.

Any of these will weaken the argument, to varying degrees.

Now, if you don't have a causal conclusion/fallacy, you need to state what the flaw is. Then, you need to find an answer that in some way relates to that flaw. A lot of times, it will just point out the flaw. Other times, it will couch it in language that tells you the assumption being made by the argument (which is just the content-specific flaw). Sometimes it will give you a specific example of when the argument breaks down as applied to a specific situation. Whatever the case, you need an answer choice that exploits that flaw.

For instance, let's look at the following argument:
We need to raise $100,000 by next Friday, or the mob will break our kneecaps. I propose that we sell drugs to raise that amount of money. In one week, we can make $120,000 selling methamphetamines. Therefore, we must sell drugs if we don't want our kneecaps busted.

The assumption here is one of exclusivity - I'm assuming that just because my plan will work, it's the only plan that will work (we MUST sell drugs).

An answer choice could say, 'The argument presumes, without providing justification, that just because a plan will work that it is the only plan that will work.'
It could also say, 'The argument assumes that the plan to sell drugs must be adopted simply because it's a possible solution to the mob problem.'
Or it could say, 'The argument ignores the fact that one member of the group has a rich uncle who would be more than willing to give them $100,000 in order to pay off their mob debts.'

The first just states the flaw; the second gets a little more specific to the argument; and the third gives me a specific other plan that would work, thus highlighting my flaw.

(Just as a note, I don't write LSAT questions, so if there's a gap in the logic I'm not seeing, just go with the overall spirit of the question)