Going Critical: Logical Fallacies

Teaching does not begin and end at the classroom doors.   It also doesn’t begin or end at our subject matter.   So often we are mentors and guides on people’s larger journeys… and which people so often don’t have the tools for.   And let me be clear:  this isn’t strictly a teachers responsibility, except that part of our jobs to show people how to think.

We live in an era where we have access to more information than in any other time in history.   The interesting things that have come out of this isn’t that people have all moved to become more enlightened, but that they have chosen how to insulate their beliefs.    Critical thinking is essential to this sort of culture, because it allows us to test whether our own ideas/beliefs or those of others have merit.   Critical thinking is necessary tool for people, and often gets overlooked because it is personally painful.    It is difficult have the intellectual and emotional honesty to admit that you are wrong.

We need to weed the damned garden, people.   Remember that you control your thoughts and ideas, not the other way around.

So:   will be the first in an ongoing series of posts about critical thinking.Straw Man

The first thing I would like to introduce are some common logical fallacies that you can use when reviewing a persons arguments.     Just to let you know, there are TONS of ways for people to make bad/misleading claims, and this list of fallacies is far from exhaustive.

  • Ad hominium – This is attacking a person rather than their argument.   “You’re stupid, so you idea sucks”
  • Post hoc ergo proper hoc – “After this therefore because of this.”   For example:   think of a study where they were cutting the legs off of frogs to see if they grew back.   The researchers then were trying to get the (legless) frogs to move around, so they were coaxing them trying to get them to move.   The frogs didn’t move.   The erroneous conclusion:   “cutting the legs off of frogs makes them deaf.”
  • Argument from authority – This is the error that having some authority or knowledge means that the person MUST be correct.   “Uncle Bob has lived in town for years.    His directions have to be right.”
  • Straw man –  This is a technique where someone counters a VERY weak (and often false) counterargument, and uses this to try to validate their own argument.
  • Ad ignorantium –  Argument from ignorance is where technique where if someone does not know that something ISN’T true, then it must be true.   “I don’t know for certain that elves are stealing my socks from the dryer.   I can’t find my socks.   I wish I could find those sock stealing elves!”
  • No True Scotsman- This is where you immediately exclude anyone who does not meet your criteria.    (Sad, but true example in my life)  When discussing (read:  I was cornered and being talked at) what made someone be saved by Christ, I was told that it was “believing in the salvation of Christ.”   When I asked if Vlad Tepesh (aka Vlad the Impaler, or count Dracula) who was devout in his beliefs was saved the reply was:   “Well, he must not be a REAL Christian.”
  • False Dichotomy – Presenting only two possible choices for an explanation or belief.    The truth is there are often MANY different possibilities, not limited to the extreme views.     For example:   Juan wanted to get a pet badly.   He was a sensitive boy, who enjoyed the quiet but who also loved to be gone all day adventuring.   Did he get a cat or a dog?   Both would make sense…    (Answer:   He got a fish).
  • Tu Quoque – Literally it means “you too.”    This is trying to validate or excuse one’s own mistakes by the mistakes of others.  “I know that beating my spouse is wrong, but Karen does it too!”


This is just a few of the ways that people mislead or are misled.   One of the best discussions I have found for the subject is “The Skeptic’s Guide:  Logical Fallacies“.

So – read a paper or listen to the news.   Especially listen to politicians or someone trying to convince you of something – and see if you can spot some bit of flim-flam that they are selling.    Oh, one important piece of information to keep in mind:   just because someones argument or reasoning is unsound doesn’t mean that their conclusion is wrong.

Now:  go forth and use your powers.

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