Prentice Hall's short list of Logical Fallacies, And More
(mostly from the 6th Edition, p. 37-38).

last updated 1/16/08

Fallacies are yet another set of reading lenses brought to us by Aristotle, and have to do with flaws in deductive logic.  They are also very audience dependent--one person's fallacy is another's truth.  Fallacies can also be quite effective in seducing certain audiences.

• Hasty Generalization: a conclusion reached with too few examples or with example that are not representative
  • Example: All women are bad drivers.  All men are in to football.  Men are from Mars.  Women are from Venus.
  • Example: Your friend complains that the phone company is run by a bunch of bumblers because they never send a bill that is correct.
• Begging the Question (circular reasoning): an argument that goes around in circles, assuming that what has to be proved has already been proved.
  • Example: when a salesperson points out that the product she is selling is "environmentally friendly," you ask why.  Her reply is that it doesn't pollute the atmosphere.  Why doesn't it pollute the atmosphere?  Because, she explains, it's environmentally friendly.
  • Example: You ask your mother why you have to do something, and she says, "Because I said so," or "Because I'm the mother."  Of course, some mothers might know more than their children, and thus they are trying to use ethos to appeal to your need for logic.
  • Example: Current Republican presidential hopefuls are all saying we need to secure the borders, but few of them are saying how to do that.  Getting specific on this issue can open their campaign up to attack (e.i. if they say they will build a border fence, they could be compared to the Soviets who built the Berlin Wall), and thus they use a lot of synonyms about securing the borders in order to stay general.
• Doubtful Cause (Post Hoc, Ergo Propter Hoc): a mistake in reasoning that occurs when one event happens and then another event happens, and people mistakenly reason that the first event caused the second when in fact no such relationship exists.  (The Latin phrase above means "after this, therefore because of this."  Also see the sort of related Causal Reductionism):
  • Example: if a school institutes a dress code and vandalism decreases the next week, it is tempting to reason that the dress code caused a decrease in vandalism, but this sequence does not prove a cause-and-effect relationship.  Other factors may be at work (maybe graffiti paint is in short supply), or incidents of vandalism might increase next week in spite of the dress code.  More conclusive evidence is needed.
  • Example: If ice cream sales go up in the summer, and drownings also go up in the summer, ice cream must cause drownings...
  • Example: The pollution coming from the Geneva Steel plant 20 years ago caused your mother's lung cancer today (obviously the steel industry would try to see this as a post hoc, but environmentalists and others would not--fallacies are thus audience dependent).
• Irrelevant Proof: non-sequitur...a line of reasoning in which the conclusion (the interpretation?) is not a logical result of the premise.
  • Example: That movie was superb because it cost so much to produce.
  • Example: My outfit is hot because I bought it in New York.
• False Analogy: if things are similar in some ways, they are similar in other ways too, but the examples really aren't similar enough.
  • Example: If engineers can design those black boxes that survive plane crashes, they should be able to build the whole plane from that same material.  (bo-ing!)
  • Example: in Michael Moore's Bowling for Columbine, he is comparing US gun murders (around 11,000 per year) to gun murders in other countries like Japan (with perhaps 1 gun murder in a year)--but they are too different than us, and thus that can be a false analogy.  He tries to choose another country that is more similar--Canada--to avoid the fallacy (not that we are totally like Canada, though, either, but it's less of a false analogy).
• Personal Attack: ad hominem...focus on aspects of the person in an attempt to dismiss
  • Example: If an economist proposes a plan for helping impoverished people, the opponent might dismiss it by saying the economist has never been poor.
  • Example: My mother said that Helen Ready, a singer from the 1970's, was a bad singer because she was a lesbian.
  • Example: Bill Clinton was a bad president because he had an affair (of course some audiences would say this is not a fallacy).
• Either...Or: establishing false either/or situation (a black and white binary) that doesn't allow for other possibilities
  • Example: Either the government balances the budget, or the country will slide into another great depression (it's way more complex than that).
  • Example: You're either with us, or you're against us.  It's the good guys vs. the "evil doers."
• Bandwagon: appears to be sound because many believe it
  • Example: in a political campaign, we might hear that we should vote for someone because many other people have decided this person is the best candidate.
  • Example: you tell your mother you want an IPod because everyone has one, and she calls you on your bandwagoning by saying, "Well, if everyone was jumping off cliffs, would you do that too?"
  • Example: Barak Obama says he is the candidate who will bring change (and isn't change something we supposedly want), so you should get on board with his campaign (this isn't egregious bandwagoning, but it is a form of it).

Here are others I like to look for:

• Oversimplification/Overgeneralization--just because you put a qualifier in front of a hasty generalization doesn't make it logical.  Many women are bad drivers?  Some?  Most?  Three?  Millions?
• Red Herring: like ad hominem, but usually not an attack on the person--a way of diverting the attention from the issue at hand.  You think poverty is an issue, but look at the travesty of Gay Marriage!
• Slippery Slope: if you outlaw guns today, tomorrow criminals and terrorists will take over the world!
• Burden of Proof: if you don't have a good argument against me, then I must be right.  If you can't find the scientific link between cancer and smoking, then smoking must be ok.

You can find oodles of other fallacious arguments at http://www.don-lindsay-archive.org/skeptic/arguments.html .