LSAT Weaken Questions – Logical Reasoning
Weaken questions can operate in a few different ways. Let’s look at some examples.
Sep 09 Exam, Section 4, #2
Here’s the basic logic given in the argument:
You can always keep your hands warm by putting on extra layers of clothing (clothing that keeps the vital organs warm).
THUS, to keep your hands warm in the winter, you never need gloves or mittens.
This argument is a sound argument – no flaws or assumptions. If you have another option for keeping your hands warm, then you never truly need gloves or mittens.
In this case, the correct answer actually attacks the main premise. The correct answer says that sometimes (when it’s really really cold) putting extra layers of clothing on actually is not enough to keep your hands warm. Notice how this contradicts the premise. So, to weaken an argument you can attack a supporting premise.
ANSWER TYPE 1: attack a premise
Sep 09 Exam, Section 4, #10
Here’s the basic logic given in the argument:
Most people don’t eat enough fruits and vegetables to get their daily requirement for vitamins.
THUS, most people need to supplement with vitamin pills.
This argument is NOT a sound argument. It makes a pretty big assumption: People can’t fulfill their daily requirement of vitamins using some other source aside from vitamin pills.
The correct answer could attack this assumption by negating it: People CAN fulfill their daily requirement of vitamins using some other source aside from vitamin pills. This would definitely weaken the argument. However, it’s more likely that the correct answer will be a little tougher to spot. Instead of just outright negating the assumption, it will probably give an example of a source of vitamins other than pills. This is exactly what the correct answer does in this case. It says that many foods that aren’t fruits and vegetables have the vitamins that fruits and vegetables have. This obviously weakens the claim that you would need pills to get those vitamins.
In this case, the correct answer attacks an assumption by introducing a counter premise. In order to see it, you’ve got to be able to spot the assumption first.
ANSWER TYPE 2: attack assumption through counter premise
Jun 09, Section 2, #9
In this case, a single claim is made without any supporting premise:
Reducing meat consumption will not significantly reduce world hunger.
In this case, the answer won’t attack a premise because there isn’t one. It’s hard to attack an assumption because we don’t have a P – C relationship (assumptions usually lie between the premise and conclusion). So, this must be a different type.
Here, the correct answer simply raises a counter premise, an outside fact that seems to indicate that the claim could be wrong: The amount of land needed to raise meat for one person could grow enough grain to feed 10 people. If this were true, maybe, just maybe, we could put a dent in world hunger by eating less meat.
ANSWER TYPE 3: introduce a counter premise.
To see if you’ve got it, take a look at section 3 (LR) of the Sep 09 exam, #24. Which of these three types is it?