©Adam vanLangenberg - MSSS Logical Fallacies 101 ©Adam vanLangenberg - MSSS

Claiming that something is true because we can’t disprove it. Ad ignorantiam Claiming that something is true because we can’t disprove it. “We don’t know what those lights in the sky are, therefore they are aliens.”

Argument from authority The idea that something must be true because it has been said by somebody with authority. “I use these magical healing crystals every day!” – Dr S. Novella, M.D.

Argument from Final Consequences Making an argument based on how good/bad the consequences are. “Aliens must exist because otherwise we would be all alone in the universe.”

Argument from Personal Incredulity Claiming that something is impossible because you personally don’t understand it. “I don’t understand how evolution works so there must be an intelligent designer.”

Argument from Antiquity Stating that something must be good because it has been used for a long time. “Of course it’s legitimate! Cave men have been doing this for millions of years!”

Argument from Popularity Stating that something must be legitimate because a lot of people believe in it. “1 million Usher fans can’t be wrong!”

Correlation vs. Causation Assuming cause and effect for two things simply because they occurred together. “I have never been attacked by a bear while wearing this tie. Bear-proof tie!”

Unexplained vs. Unexplainable Believing that because we cannot explain some phenomenon now, we will never be able to explain it. “We don’t know what the Voynich Manuscript means so it must have been written by angels!”

False Continuum Thinking that because no distinct line exists between two extremes, then those two extremes are really the same thing. “There’s a fuzzy line between religions and cults, so all religions must be cults.”

“Either you are with us, or you are with the terrorists.” False Dichotomy Insisting that things must either be one way or another. “Either you are with us, or you are with the terrorists.”

Applying criteria to one thing but not to another. Inconsistency Applying criteria to one thing but not to another. “Prescription drugs need to be strongly regulated but herbal supplements do not.”

Making a conclusion that doesn’t follow from the arguments. Non-Sequitur Making a conclusion that doesn’t follow from the arguments. “God is love. Love is blind. Ray Charles is blind. Therefore Ray Charles is God.

Post-hoc ergo propter hoc Saying that because A happened before B, A must have caused B. “A rooster crows before the sun rises so the rooster’s crowing must cause the sun to rise. Clever rooster!”

Extending an argument to an absurd conclusion. Reductio ad absurdim Extending an argument to an absurd conclusion. “If you don’t believe in aliens because you haven’t seen one, how can you believe in France? You haven’t seen it either.”

“Your argument is wrong because you’re a big fatty fat fat.” Ad hominem (My favourite) Attacking a person, rather than their claims. “Your argument is wrong because you’re a big fatty fat fat.”

Slippery slope Arguing that believing something must also involve believing in its extreme. “If you support the death penalty then you must also support genocide.”

Arbitrarily introducing something into an argument to make it work. Special pleading Arbitrarily introducing something into an argument to make it work. “My psychic powers didn’t work because of all the sceptics in the room! Also, because of magnetic interference.”

Straw man Twisting your opponent’s argument to make it easier to argue against. “I think homeopathy is stupid and should be banned.” “So you think we should ban medicines, do you?”

“Go to bed.” “Why?” “Because I said so.” Tautology The argument that A = B because A = B. “Go to bed.” “Why?” “Because I said so.”

Moving the goalpost “…and that is why your mother is fat.” After losing an argument, throwing something else into the ring which cannot yet be proven. “…and that is why your mother is fat.” “Oh yeah? Well then what is she eating right now?”

“You can’t say murder is wrong, you’re a serial killer!” Tu quoque Attacking somebody for arguing against something that they used to do. “You can’t say murder is wrong, you’re a serial killer!”

“It is McDonald’s fault that I am fat!” Begging the question Not stating something important that your argument assumes. “It is McDonald’s fault that I am fat!”