Logical Fallacies

Logical Fallacies Fallacies are common errors in reasoning that will undermine the logic of your argument. Fallacies can be either illegitimate arguments or irrelevant points, and are often identified because they lack evidence that supports their claim. Avoid these common fallacies in your own arguments and watch for them in the arguments of others.

Appeals to authority Appeal to Authority: Instead of providing evidence the rhetor simply appeals to the respect people have for “experts.” Testimony from an authority may be a fallacy unless: The authority is actually an expert in a specific field The authority is arguing a point well-accepted in the field The authority is objective and unbiased.

A Common Appeal to “authority” Appeal to Authority: Instead of providing evidence the rhetor simply appeal to the respect people have for the famous. Matthew Mcconaughey saying he “just liked” a car doesn’t mean it’s a quality car. What makes him an expert on cars? Click Here for video.

Straw Man Straw Man: This move oversimplifies an opponent's viewpoint and then attacks that hollow argument. It is much easier to win an argument with a scarecrow than a reasonable opponent.

Straw Man Straw Man: This move oversimplifies an opponent's viewpoint and then attacks that hollow argument. Original Argument: Texting and driving is dangerous and therefore texting drivers should be fined. Straw-man Counter: These fines are insane! People need cell phones in cars to make emergency calls.

Circular Reasoning Circular Argument: This restates the argument rather than actually proving it. Example: Carpool lanes really improve traffic congestion because they greatly reduce the number of cars on the road.

Begging the Question Begging the Claim: The conclusion that the writer should prove is validated within the claim. Example: Filthy, polluting hummers should be banned.

Slippery Slope Slippery Slope: This is a conclusion based on the premise that if A happens, then eventually through a series of small steps, through B, C,..., X, Y, Z will happen too. Basically equating A and Z. So, if we don't want Z to occur, A must not be allowed to occur either. Example: If we ban Hummers because of environmental concerns eventually the government will ban all cars, so we should not ban Hummers.

Slippery Slope Click here for video.

Another Slippery Slope Click here for video.

Yet Another Slippery Slope Click here for video.

Hasty Generalization 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: My 80 year old grandmother got into a car accident last week. People over 80 shouldn’t be able to drive.

Post hoc (ergo propter hoc) AKA Cause and Effect Fallacy Post hoc ergo propter hoc: translates to “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 rode the light rail, and now I am sick. Riding the light rail must have made me sick.

Post hoc (ergo propter hoc) AKA Cause and Effect Fallacy Click here for video

Non Sequitur: “Does Not Follow” Non Sequitur: translates to “Does not follow.” It means that a the rhetor has drawn a conclusion that does not logically follow the premises. Premise 1: My neighbor’s Prius gets amazing gas mileage. Premise 2: My neighbor’s Prius has a sick paint job with flames. Conclusion: If I get a sick new paint job on my car it will dramatically improve my gas mileage.

Genetic Fallacy 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.

Either /Or Either/or: 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.

Ad hominem Ad hominem: This is an attack on the character of a person rather than his or her opinions or arguments. Example: Green Peace’s proposal for fuel efficiency guidelines are a horrible idea because they are all dirty, lazy hippies.

Ad Populum Ad populum: 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.

BandWagon Bandwagon: The argument that since something is popular or everybody is doing it, so should you. Think of peer pressure or popularity as being the basis of the argument.  Example: You should buy a Toyota Camry. It has long been the best-selling car in America.

Red Herring Red Herring: This is a diversionary tactic that avoids the key issues, often by avoiding opposing arguments rather than addressing them. Example: The light rail system might improve traffic congestion, but think of all the hard working auto mechanics who could lose their jobs.

Putting It All Together Click here for video