Logical Fallacies 101

1. Logical Fallacies 101 Adam vanLangenberg MSSS

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

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

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

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

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

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

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

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

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

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

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

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

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

15. Extending an argument to an absurd conclusion. Reductio ad absurdim “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.”

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

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

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

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

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

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

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

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