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   II. Argument Structure

Is the text an argument? An argument here doesn't mean a dispute or controversy. It means an attempt to provide a reason for believing something by citing something else. It is an attempt to show that something is true, or probably true, by appealing to something else, some reason or evidence, which indicates that it is true.

You see arguments everyday in advertisements, where companies are making arguments to persuade you to buy their product:

A LSAT course will teach you how to attack the common LSAT question types so that you can beat the LSAT. You should therefore buy a LSAT course.

In many of the Critical Reasoning questions, there will be a gap between the premises and the conclusion--the assumptions.

Premise(s) + Assumptions = Conclusions (inferences)


Target: Assumptions
On many critical reasoning questions, the question will turn on assumptions. Premises (evidence) on the LSAT will never be false. So you don't have to worry about that. The conclusion is often stated, so the whole game usually revolves around the assumptions.


Let's look at an argument to buy a LSAT course.

A LSAT course will teach you how to attack the common LSAT question types so that you can beat the LSAT. You should therefore buy a LSAT course.

Premise: A LSAT course can teach you how to attack the common LSAT question types.
Conclusion: You should therefore buy a LSAT course.

There are some "assumptions", "errors" or "gaps" in that statement:

  1. A LSAT course can teach you common question types, but not all question types. A LSAT course can try to prepare you, but obviously a course can't prepare you for every past question that has appeared on the LSAT.
  2. The LSAT comes up with new questions all the time, so it is possible that you can come across a question that no one has seen before.
  3. A LSAT course may have the content, but will you have the willpower to use it?


    Valid vs. True
    The LSAT is looking for valid arguments, not necessarily true ones. A valid argument follows from its premises.

    An ostrich is a bird
    All birds fly
    Conclusion: an ostrich can fly

    The above argument is valid, but not true. Try not to argue or bring in external knowledge to the LSAT, where you are just looking for valid arguments, given the information that they have given you.

    Why are flying ostriches so important to skilled critical thinking?

    In this chapter we regularly discuss absurd things. This isn't entirely for humorous effect. Skilled critical thinkers often employ the argument ad absurdum, which means taking a logical argument and stretching it to its breaking point to determine its validity. In this case, we use flying ostriches to show that arguments may be true but not valid.


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