LSAT Logical Fallacies

This lesson covers common logical fallacies. A few questions on the LSAT test will ask you to identify flaws in the reasoning of an argument. Learning these fallacies will help you quickly get those points. Moreover, learning the structure of these common errors will give you greater facility in dealing with arguments in general.

This is the first in a series of lessons covering LSAT Logical Fallacies. The series includes the following articles:

• LSAT Logical Fallacies: an introduction
• Common LSAT Flaws
• Secret LSAT Logic Flaws

LSAT Logical Fallacies

A quick caveat about LSAT logical fallacy names: The only formal terms the LSAT uses to describe logical flaws are “begging the question,” and “circular reasoning.” That is, the LSAT will not present you with an answer choice that says, “ad hominem attack.” Instead, the answer choice will say, “the author attacks the person arguing for reform, not the reform policy itself.” It’s more important that you learn how an argument can fail than to learn all the technical names for the fallacies. Furthermore, don’t ever use these terms in your everyday conversations. If you walk around telling people, “I cannot contribute to the football pool based on your appeal to pity,” no one’s going to invite you to the Super Bowl party.

Almost all of the arguments on the LSAT are flawed in some way, generally involving the central assumption. As you practice through this course you are gaining an intuitive ability to spot that flawed central assumption. TestSherpa students call this “finding the red flag,” but it essentially means that your intuition is pointing you toward a flaw in the author’s reasoning. That flaw tips you off for all the following types of questions:

• Assumption: If the central assumption is usually flawed, find the flaw and find the assumption
• Weaken: attack the flawed assumption to weaken an argument
• Strengthen: cover up the flawed assumption to strengthen an argument
• Find the Flaw: score a couple quick points thanks to your TestSherpa foundation
• Parallel Reasoning: find an argument flawed in a similar way

The main reason you want to be familiar with logical fallacies is to recognize red flags in the argument. Most arguments on the LSAT  are flawed in some sense. A red flag pops up in your mind as you read the argument and that flag is related to the central assumption. Most questions on the LSAT deal with assumptions and flaws.
 
Very few arguments on the LSAT are completely logical. Most of them contain at least on central assumption, and most of the assumptions are somehow flawed. You have a feel for why the argument is wrong, and you use that intuition to guide you to the assumption.

In the next article, we’ll look at the most Common LSAT Flaws.