Logical Fallacies

Slippery Slope The argument that some event must inevitably follow from another without any rational claim. If we allow A to happen then Z will eventually happen, therefore we should not allow A to happen. Example: If we ban Hummers because they are bad for the environment eventually the government will ban all cars, so we should not ban Hummers. If we legalize gay marriage then we will also allow marriage between a human and an animal, a human and a car, etc. So, we should not legalize gay marriage.

Hasty Generalization This is a conclusion based on insufficient or biased evidence. In other words, you are rushing to a conclusion before you have all the relevant facts. Example: Even though it's only the first day, I can tell this is going to be a boring course. Michael Brown was shot and killed by a white cop, therefore all white cops are racist.

Post Hoc Ergo Propter Hoc (Latin: “after this, therefore because of this”) This is a conclusion that assumes that if 'A' occurred after 'B' then 'B' must have caused 'A.' Example: I drank bottled water and now I am sick, so the water must have made me sick.

Genetic Fallacy This conclusion is based on an argument that the origins of a person, idea, institute, or theory determine its character, nature, or worth. Example: The Volkswagen Beetle is an evil car because it was originally designed by Hitler's army.

Circular Argument This restates the argument rather than actually proving it. Example: President Obama is a good communicator because he speaks effectively. The belief in God is universal. After all, everyone believes in God.

Either/or (False Dilemma) This is a conclusion that oversimplifies the argument by reducing it to only two sides or choices. Example: We can either stop using cars or destroy the earth. You are either with God or against him. If you’re not with us, you’re against us.

Ad hominem (Latin: “to the man” or “to the person”) This is an attack on the character of a person rather than his or her opinions or arguments. Example: Green Peace's strategies aren't effective because they are all dirty, lazy hippies. Why should we listen to Jenny talk about the importance of sex education in elementary school when she was once arrested for a DUI?

Argumentum ad populum (Latin: “appeal to the people”) This is an emotional appeal that speaks to positive (such as patriotism, religion, democracy) or negative (such as terrorism or fascism) concepts rather than the real issue at hand. Example: If you were a true American you would support the rights of people to choose whatever vehicle they want. One common version is the “Bandwagon Fallacy.” This is used when the arguer tries to convince the audience to do or believe something because everyone else (supposedly) does. Example: Gay marriages are just immoral. 70% of Americans think so!

Red Herring This is a diversionary tactic that avoids the key issues, often by avoiding opposing arguments rather than addressing them. There is a lot of commotion regarding saving the environment. We cannot make this world an Eden. What will happen if it does become Eden? Adam and Eve got bored there!

Straw Man This move oversimplifies or ignores an opponent's viewpoint and then substitutes a distorted or misrepresented version of that argument to make it easier to attack. Example: People who don't support the proposed state minimum wage increase hate the poor. A: Sunny days are good. B: If all days were sunny, we'd never have rain, and without rain, we'd have famine and death.

Moral Equivalence This fallacy draws comparisons between different, usually unrelated topics, to make a point that one is just as bad as the other or just as good as the other. Example: That parking attendant who gave me a ticket is as bad as Hitler.

Ways to fix fallacies in your argument Pretend you disagree with the conclusion you’re defending. What parts would seem easy to attack? Pay attention to strengthening those parts. Broad claims need more proof than narrow ones. Claims or arguments that use words like “all,” “none,” “every,” “always,” “never” can be appropriate, however they require more proof and evidence. Always double check the characterizations of your opponent to make sure they are accurate and fair.