inFact with Brian Dunning inFact with Brian Dunning


Logical Fallacies 1

Think you know how to use and recognize logical fallacies in arguments? Here's how. Part 1.

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In this first of three videos, we're going to look at some common fallacious arguments; ways that people make their points sounds convincing even when they're not true. A common one is:

The Ad Hominem

Arguing against the person rather than against the argument. Let's say some guy is trying to convince you that Einstein's theory of relativity is wrong:

Einstein? That guy married his cousin. How can you trust his calculations?

Flip it around and you have:

The Bandwagon Fallacy

Which tries to claim that something must be true because so many people believe it:

50 million people have read The Secret. That many people can't be wrong.

Oh yes they can. How about the people whose religious or political beliefs are different from yours? That's a lot more than 50 million right there.

You can also use:

The Argument from Antiquity

To prove that something must be true because people have believed it for a long time.

Chinese medicine's been around for 5,000 years. It wouldn't have lasted that long if it didn't work.

Being ancient only proves that an idea comes from prescientific times. Maybe it works, like the wheel; maybe it doesn't, like burning witches (some more great ancient wisdom).

A related tactic is to pull out

The All-Natural Fallacy

This is a way to sell a product by raising the specter of concern about competing products that might be... "tarnished" by modern knowledge.

You should sprinkle some of this Haitian zombie powder in your wound. Ground human bones, hemlock, stinging nettle, pufferfish neurotoxin... it's all natural.

The Argument from Authority

Ignores the need to have good information and instead relies on an authority figure.

It doesn't matter what your research shows; my information came from a scientist. So it can't be wrong!

But if all else fails, fall back on:

The Appeal to Quantum Physics

This is why people think Deepak Chopra knows anything; he throws around terms like this to make whatever he says sound scientific and advanced.

Quantum physics links our metaphysical beings through quantum entanglement.

Hey it sounded over my head; he must know what he's talking about.

Next time we'll look at some ways that language itself can be misused to accomplish the same thing.

— Brian Dunning

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References & Further Reading

Clark, J., Clark, T. Humbug! The skeptic's field guide to spotting fallacies in thinking. Brisbane: Nifty Books, 2005.

Damer, T. Edward. Attacking Faulty Reasoning: A Practical Guide to Fallacy-Free Arguments. Belmont CA: Wadsworth Publishing Company; 3rd edition, 1995. 224.

Miller C., Miller, D. "On evidence, medical and legal." Journal of American Physicians and Surgeons. 1 Sep. 2005, Volume 10, Number 3: 70-75.

Randi, James. "SYLVIA BROWNE ON THE ROPES." Swift - Weekly Newsletter of the James Randi Educational Foundation. James Randi Educational Foundation, 2 Feb. 2007. Web. 18 Oct. 2007. <>

Sagan, C. The Demon-Haunted World: Science as a Candle in the Dark. New York: Random House, 1995.

Walton, D. Informal Logic: A Handbook for Critical Argumentation. Cambridge/New York: Cambridge University Press, 1989.


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