Which one of the following statements most accurately characterizes a difference between the two passages?

on February 11, 2018

false premise

I thought for this exam we were always supposed to assume the premises are true? That is what we were told in my other LSAT classes

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Mehran on February 14, 2018

That is correct. We say the same thing.

Attacking an argument by pointing out a premise is false is far too easy.

The LSAC is not likely to test this skill.

The more likely skill they will test is the idea of "so what?" i.e. so what if the premises are true, that doesn't necessarily mean the conclusion follows because . . .

Hope that helps! Please let us know if you have any other questions.

Bradley on February 20, 2019

I have a similar question. I believe we're referring to the Boy named Sure example (nice touch btw). In that scenario, the argument IS valid IF the premises are assumed true. However, because "not all boys are named sue" the argument was then considered to be invalid. In short, are we always supposed to assume that the premises are true? Or if we know that a premise is factually false, can we consider an argument illogical for that reason?

Katherine on February 20, 2019

Hi @BradG,

As the lesson discusses, an argument is valid if and only if the conclusion follows logically from the stated premises, assuming those premises are true.

The “Boy Named Sue” example was meant to show one of the ways you can prove argument is invalid - identifying a false premise. In this case, we know that the premise “Anyone named Sue is a girl” is false. Because there is a false premise, the argument is invalid. Although this is one way to attack an argument, it should not be our focus for purposes of the LSAT.

For purposes of the LSAT, focus on whether the conclusion follows logically from the stated premises. In the example given in the lesson the premise is “It is cold” and the conclusion is “It will snow.” That is a flawed argument because the conclusion does not necessarily follow from the premise. We know that sometimes it is cold but doesn’t snow! We didn’t take issue with whether or not it was cold. Instead, we had to assess the next step, involving critical thought. The “so what?” question Mehran mentioned above.

Because the LSAT test makers are more likely to test your ability to asses the logical connection between premise and conclusion, focus on that method of attacking an argument. Unless a question specifically asks you assess an argument’s premises, you may assume they are true.

I hope this helps!

Bradley on February 20, 2019

Makes more sense.

Thank you!

Ravi on February 21, 2019

@BradG happy to hear it makes more sense! Let us know if you have any more questions!