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3 Ways to Spot Logical Fallacies

3WaysToSpotLogicalFallacies
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A fallacy is simply a false or mistaken idea.  If you can spot logical flaws, you can save yourself from bad information.  This includes defending yourself from politicians, sales people, diet books, doctors, and even your own kids.  In logical arguments, where logic matters, it’s important to avoid your own logical fallacies, as well as spot them in counter-arguments.  In rhetoric, your overall persuasion is more important than logic.  While logic plays a role, it’s also about emotion and character (see Character Trumps Emotion Trumps Logic.)   The key thing is don’t start trying to spot logic fallacies in all your conversations.  Instead, spot fallacies when logic really counts such as a logical debate or when you are making important decisions based on information based on logic.

In Thank You for Arguing: What Aristotle, Lincoln, and Homer Simpson Can Teach Us About the Art of Persuasion , Jay Heinrichs writes about detecting logical fallacies.
Key Take Aways
Here’s my key take aways:

  • Distinguish between rhetoric and logic.  In logical arguments, it obviously matters whether your logic is right.  In rhetoric, logic isn’t as important as persuading.  You can even be wrong in your logic.  
    Bad proofs, wrong number of choices, or a disconnect between the proof and conclusion.  To spot logical fallacies, look for bad proof, the wrong number of choices, or a disconnect between the proof and the conclusion.
  • Identify bad proofs.  A bad proof can be a false comparison.  It’s the apples and oranges issue.  It can also be a bad example that just isn’t relevant.  Another example if using the lack of examples proves something.
  • Identify the wrong number of choices.  This one is easy to spot.  Anytime there’s a number of items you need to question whether it’s the right set.  For example, are there only 3 ways to spot logical fallacies?  In a logical argument, this could be important.  In rhetoric or persuasion, what’s more important is whether anybody cares that you have the right number of options and whether it’s limiting. For example, somebody might only see two ways to do something, but you might have a third alternative.
  • Identify disconnects between proof and conclusion.  This is the classic, “jumping to conclusions.”  The key question is, does the proof really lead to the conclusion?  For example, is it simply a correlation or is it causation?

Once you know what to look for, spotting logic flaws is a lot easier.  When you don’t know what to look for, it’s easy to get tripped up, or mislead, whether intentionally or unintentionally.  Before you start calling fowls though, you should figure out whether debating the logic is worth it, based on the context and your situation.

Why Spot Logical Fallacies
Why should you learn how to spot logical fallacies?  On a very practical level, it’s how you can defend yourself from bad information or bad arguments.  If you don’t fall for the bad arguments or bad information, it doesn’t matter as much, unless it’s formal logic.  In formal logic, the attitude and rules are strict.  In rhetoric, there really are no rules.  Your audience is responsible for finding the flaws.  If they do find flaws in your logic, you lose credibility.  Heinrichs says that the ability to find logical fallacies is how you defend yourself from politicians, salespeople, diet books, doctors and even your own children.
3 Ways to Spot Logical Fallacies
There’s 3 simple ways you can spot logical fallacies:

  1. Bad proofs. 
  2. Wrong number of choices. 
  3. Disconnect between proof and conclusion.

Bad Proofs
This includes three sins:

  • The false comparison, such as lumping examples into the wrong categories.
  • bad examples
  • ignorance as proof, such as asserting that the lack of examples proves something.

Wrong Number of Choices

This is the case where you simply don’t have the right number of choices.  Either you are offered two choices when there’s actually more, or three choices are merged into one.
Disconnect Between Proof and Conclusion
This includes:

  • The proof and conclusion are identical
  • The red herring (a distraction)
  • The wrong ending (the proof fails to lead to the conclusion)

Additional Resources
For more information, check out:

My Related Posts

6 Comments on "3 Ways to Spot Logical Fallacies"

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  1. J.D. Meier's Blog : Spotting Logical Flaws | January 28, 2009
  1. JD,
    I like the simple practice of spotting the Logical Fallacies.
    While my intuition usually helps me here a lot, having good pattern is always helpful.

    Next time when my intuition tells me something wrong i can simply ask myself:
    1. Is the proof good enough?
    2. Am I offered good number of choices?
    3. Am I presented with the proof with actual problem?

    Good stuff, liked it. Simple and very practical!
    Got you right?

  2. J.D. Meier says:

    Hey Alik

    Thank you. Yes, you got it.

    While it sounds simple, putting it into practice can be tough. The one I find the easiest to spot is the wrong number of choices. While I find it easy to spot gaps between proof and conclusion, I find it hard to figure out the data or the tests that will lead from A to B.

  3. I think the older I’ve gotten the better I am at tuning into fallicies. Do you find that the same for you? Maybe it’s just a maturing thing?

  4. “before you start calling fowls…”

    I think you mean fouls. The argument may be a turkey, but rules are rules.

  5. Fem Ezek says:

    Please identify the fallacy in this statement; If a person is a teacher then, he must have been well trained. Ahmed is no doubt well trained. Ahmed is a teacher.

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