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.

We must learn to avoid these in our own arguments and be able to spot them in the arguments of others.


Circumstantial evidence: We cannot rely on circumstantial evidence. Even when it happens to be right, it is wrong because it is circumstantial evidence.

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. 
This method is often used in court to jump to conclusions.

If we ban Hummers because they are bad for the environment eventually the government will ban all cars, so we should not ban Hummers.
Eg This red apple is poisonous and will kill you if you eat it. Therefore you should not eat any red apples as they are poisonous and can kill you.
If you smoke cannabis you'll get bored and move onto other drugs. Weed is a gateway drug

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.

Eg. Thinking someone is a loser judging only their looks.

Post hoc ergo propter hoc: 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.

Eg. Shawn got punched in the eye yesterday, today he's not in school and it must be because of yesterdays incident.

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.

She's good at maths because she's Asian.

Begging the Claim: The conclusion that the writer should prove is validated within the claim. Example:

Filthy and polluting coal should be banned.

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Circular Argument: This restates the argument rather than actually proving it. Example:

George Bush is a good communicator because he speaks effectively.

She's a good athlete because she is fit.

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.

One can either stop eating fast food or face obesity.

Ad hominem: 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.

His lessons are so boring because he is not motivated.

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.

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Red Herring: This is a diversionary tactic that avoids the key issues, often by avoiding opposing arguments rather than addressing them. Example:

The level of mercury in seafood may be unsafe, but what will fishers do to support their families?

Straw Man: This move oversimplifies an opponent's viewpoint and then attacks that hollow argument.

People who don't support the proposed state minimum wage increase hate the poor.

Hearsay- Where you pass information which you have heard from somebody else.
I heard that she will not be coming to school for 3 weeks from Suzan.

Moral Equivalence: This fallacy compares minor misdeeds with major atrocities.

That parking attendant who gave me a ticket is as bad as Hitler.

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