Identifying Logical Fallcies

John Madden and Robert Finstad

When analyzing an argument by a writer or speaker, it is essential to consider the validity of said arguments. It is not uncommon for writers or speakers to intentionally or unintentionally use fallacies in their arguments.

Appeal to Authority - The writer cites some authority to support their claim, but the authority is not an expert on the subject.

Example: Paris Hilton declared that Al Gore's economic reforms would cause another reccssion.

Straw Man - The writer distorts the oppositions argument into an easily attack-able position, and then tears down this false position.

Example: Those who do not support this new economic reform want the economy to fail.

Presupposition: The writer supposes some information and then draws a desired conclusion from it, without first confirming the information.

Example: Everyone in this class wants better computers to write on their blog, therefore we should spend money upgrading the computer lab.

Either-Or Fallacy - The writer simplifies the argument to an either-or choice, when their may be several different choices.

Example: Either we invade Vietnam to stop communism, or we let communism control Vietnam.

Slippery Slope - The writer argues that if we allow something to occur, there will be further undesirable results that will follow.

Example: If we allow the government to separate church and state, the government will eventually abolish organized religion.

Circular Reasoning - The writer uses the conclusion of the original argument to defend the original argument.

Example: My research paper was written well because I am a good writer.

Appeal to Force - Where the writer/author proposes a negative consequence if the claim is not believed.

Example: If you don't do your chores you will be grounded for a week.

Attacking the Speaker - This is an attack on someones character rather then on their arguments or opinions.

Example: Jeff's opinions and arguments about sentence structure cannot be right because he is a math major.

Hiding Information/Half Truths - When a writer creates a conclusion without stating all relevant facts to that argument.

Example: I had the highest score in my computer science class!
                -It was not disclosed that this computer science class was an independent study course.

Hasty Generalization - Rushing to a conclusion with insufficient or biased evidence.

Example: The first week of class was so difficult that if I don't drop it now I'll fail it!


This information is based on the following sources:

http://owl.english.purdue.edu/owl/resource/659/03/ (Accessed 9/17/2012)
http://leo.stcloudstate.edu/acadwrite/logic.html (Accessed 9/17/2012)
The Bedford Handbook 7/e by Diana Hacker (Copyright 2006)