What to Know About Logic on the LSAT

What to Know About Logic on the LSAT
New students to the LSAT might wonder what they need to know about logic for the test. If you haven’t studied logic or philosophy in school, it might feel a little daunting to suddenly learn it now. But don’t worry, you don’t need to have a degree in philosophy to do well on the LSAT. Take a look at this introduction to logic on the LSAT.

What is Logic on the LSAT?

In short, logic is the study of the basic ideas and methods we can use to tell the difference between good reasoning and bad reasoning. And what is reasoning? Well, to put it simply, it’s thinking sensibly. So if you can think logically, you can think sensibly.

In the end, the goal of all who are interested in logic is to use solid, agreed-on methods to come to well-supported conclusions.

Why is Logic on the LSAT?

Using logic is fundamental to law. So, it makes sense that the Law School Admissions Test should test your skills in it! When faced with proving or disproving a case, lawyers must use solid arguments and facts to support a conclusion. Let’s say there was a law that says one is guilty of “X” if there were three components of their crime. In other words, “If A, B and C, then –> Guilty of ‘X.'” To prove a person guilty of “X,” a lawyer has to show, with a solid argument, that A, B, and C were part of the crime. The judge would definitely ignore things like irrelevant emotional pleas and name-calling in court. These are examples of flaws of reasoning, or fallacies, that are not correct ways to make a solid argument.

Premises and Conclusions–Building Blocks of Arguments

On the LSAT, especially on the Logical Reasoning section, you’re going to come across tons of short arguments. How will you know that you’re reading an argument? Well, generally, you can tell that there’s an argument being made if the sentences build up to a statement that someone wants everyone to believe. For example, “Smoking causes cancer. Smoking is expensive. Therefore, smoking is bad.”

So here you can see that someone trying to convince you of their conclusion–that smoking is bad. What are their reasons? Well, number 1–smoking causes cancer, Number 2–smoking is expensive. These statements, or propositions, support the conclusion. We call these the premises of the argument.

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When evaluating a conclusion, ask yourself, “Were the reasons for this conclusion good?” “Does the conclusion follow from the premises?” To say that a conclusion “follows” from the premises means that the conclusion definitely makes sense and should result from the premises if they’re true.

In this smoking example, do you think the conclusion definitely follows from the premises? May be not! Sure, you can point out that smoking is expensive. But someone else might say that not all expensive things are bad. And that is true! Just because something’s expensive doesn’t mean it absolutely has to be avoided. (Lots of great things are also expensive.)

So in this case, one might have to add a few premises to strengthen the argument. They could add the premises that “Cancer is bad. Spending too much on expensive and unnecessary things is bad.” And finally, “Anything that has two bad consequences can be called bad.” That would really solidify the conclusion that “smoking is bad.”

The Order of Premises and Conclusions for Logic on the LSAT

It’s very important to be comfortable with all the ways you might find premises and conclusions in arguments on the LSAT. This is particularly true on the Logical Reasoning section. The test-makers can make a question more difficult by switching up the order of these statements. Clearly, the test would be a lot easier if we could always expect the premises to come before the conclusion. (It’s a pretty natural order!)

Conclusion-First Argument

The city should build a new bridge. The old bridge is damaged beyond repair and the city’s economy cannot prosper without all roads in top shape.

Conclusion-in-the-Middle Argument

The hurricane’s winds will reach 140 mph and will drop tons of rain. Mobile home residents should evacuate immediately. After all, mobile homes are not safe in the face of strong winds and heavy rain.

Same-Sentence Argument

Mayor Johnson has been our longest serving mayor, thus he’s the best we’ve ever had.

As you can see, there are plenty of ways you can read an argument on the LSAT. So, remember to keep an open mind and to find the conclusion, try to get to the bottom of what point someone might convinced of.

Flawed Logic on the LSAT

As you can see, knowing both what a good argument looks like and what a bad argument looks like are really key to your success when it comes to logic on the LSAT. It might be simple to recognize when an argument makes sense, but most students new to the LSAT might not realize that some argument methods are actually reasoning flaws. There are several “rules” of logic that should ideally be followed to show that you’re making a good argument. If you break these rules, you’re likely committing a flaw.

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One of the ways your argument can fail is if it’s premise doesn’t lead to the conclusion. That is, if a conclusion could still be false even if all it’s premises were true, the argument has failed. In the case of logical fallacies, they often seem to be correct ways to argue, but they’re not.

For example, fallacies often have to do with relevance. Your premises should be directly relevant to your conclusion. So, if you argue against your opponent by attacking them (the Ad Hominem fallacy), you’re probably not making a point that is relevant to the truth of your conclusion, and this is a flaw.

How to Improve Your Logic on the LSAT

The best way to attack the arguments you’ll find on the LSAT is to build your foundation. Magoosh Online LSAT Prep provides all the lessons you’ll need to feel comfortable with logic on the LSAT. You’ll be able to work on your diagramming skills, knowledge of common reasoning flaws, and comfort in reading arguments of all forms. Sign up today!

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