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David Blomstrom

What are Copi's 18 Core Fallacies?

Kind of a dumb question, but I've seen so many references to "18 core fallacies" listed in Irving Copi's 1961 book Introduction to Logic, but every online reference I check lists 15.

I could buy his book from Amazon, but it isn't available as an epub - just a $65 paperback. (I finally purchased Dr. Bo's book, by the way.)

I know Copi's book isn't the current reference, but I'm still curious to know what the 18 magic fallacies are. Does anyone have the complete list?

Thanks.

asked on Thursday, Feb 25, 2021 02:30:47 PM by David Blomstrom

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Bo Bennett, PhD writes:

I never came across this in the 9+ years I have been collecting fallacies.

posted on Thursday, Feb 25, 2021 03:11:23 PM
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David Blomstrom writes:

Just to be clear, are you saying that you've seen his book, but you - like me - have never found a list of 18 fallacies?

If so, this is almost humorous. There's a small army of fallacy experts out there raving about this magic list of 18 "core fallacies" when there's only 15. ;)

It probably isn't important, as it sounds like his book is no longer the Bible. I was just curious.

Thanks.

posted on Thursday, Feb 25, 2021 03:15:24 PM
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TrappedPrior (RotE) writes:
[To WebRanger]

According to Stanford Encyclopedia of Philosophy, there are 18.

[ login to reply ] posted on Friday, Feb 26, 2021 07:27:55 AM
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Bo Bennett, PhD writes:
[To WebRanger]

I have never seen the book nor heard of any magic number, either.

[ login to reply ] posted on Friday, Feb 26, 2021 07:33:54 AM
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David Blomstrom writes:

Yes, I consulted Stanford. It does say there are 18 core fallacies - but it only lists 15. -- https://plato.stanford.edu/entries/fallacies/#CorFal

There are other websites that do the same thing. They tell you there are 18 core fallacies, then list just 15.

Are they lying about the number of core fallacies, or did they forget three of them?

It looks to me like someone made a mistake, and other people just copied and pasted the information without thinking about it. Would this qualify as an Internet rumor, or whatever it's called? ;)

posted on Friday, Feb 26, 2021 07:33:44 AM

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Answers

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Jordan Pine
3

Update: According to the 14th edition of Irving M. Copi's "Introduction to Logic," which I now own in PDF form, there are 19 logical fallacies:

  • 7 fallacies of relevance (the appeal to the populace, the appeal to emotion, the red herring, the straw man, the attack on the person, the appeal to force and missing the point/irrelevant conclusion)
  • 4 fallacies of defective induction (the argument from ignorance, the appeal to inappropriate authority, false cause, hasty generalization)
  • 3 fallacies of presumption (accident, complex question, begging the question)
  • 5 fallacies of ambiguity (equivocation, amphiboly, accent, composition, division)

I suspect earlier editions had 18 (or later editions since I have seen a 15th edition book cover), and earlier editions had 15. That's the cause of the confusion.

Soon I will own a used hardcover of the 3rd edition and will report back to you what I find.

answered on Friday, Feb 26, 2021 11:12:50 AM by Jordan Pine

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Jordan Pine
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Update #2: I now have a copy of the third edition of Irving M. Copi's "Introduction to Logic."

You'll recall that there are currently 15 editions of this book and that in the 14th edition, there are 19 logical fallacies:

  • 7 fallacies of relevance (the appeal to the populace, the appeal to emotion, the red herring, the straw man, the attack on the person, the appeal to force and missing the point/irrelevant conclusion)
  • 4 fallacies of defective induction (the argument from ignorance, the appeal to inappropriate authority, false cause, hasty generalization)
  • 3 fallacies of presumption (accident, complex question, begging the question)
  • 5 fallacies of ambiguity (equivocation, amphiboly, accent, composition, division)

 

In the much earlier third edition, there are 18 fallacies:

  • 13 fallacies of relevance (the appeal to force, the attack on the person-abusive, the attack on the person-circumstantial, the argument from ignorance, the appeal to pity, the appeal to the populace, the appeal to authority, accident, hasty generalization, false cause, begging the question, complex question, irrelevant conclusion)
  • 5 fallacies of ambiguity (equivocation, amphiboly, accent, composition, division)

Comparing the two, it seems several of the "fallacies of relevance" were later broken out into two separate categories: "fallacies of defective induction" and "fallacies of presumption." In addition:

  1. The attack on the person (ad hominem) was collapsed into one fallacy in later editions (-1=17)
  2. The red herring was added (+1=18)
  3. The straw man was added (+1=19)

And that is how "18 core fallacies" became 19. Not sure why online lists reference 15. Perhaps that is the count in yet another edition!

answered on Tuesday, Mar 09, 2021 05:04:24 PM by Jordan Pine

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David Blomstrom writes:

Wow, thanks so much for that info!

It sounds like people just started copying the 15 fallacies reference without actually checking it, turning it into an Internet rumor, or whatever it's called.

It also sounds like Irving Cope's was the most important milestone in the last few centuries, until Hamblin shook things up. But it seems to me we're due for another update.

I should probably give Edward Bernays his dues, too. I saw some references to him while researching appeals to emotion.

posted on Tuesday, Mar 09, 2021 05:31:59 PM
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Jordan Pine
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Wow. I hadn’t heard of this book, either, but color me impressed!

”For more than six decades, and for thousands of students, Introduction to Logic has been the gold standard in introductory logic texts ...

“Irving M. Copi was a logician who studied under Bertrand Russell while at the University of Chicago. He held appointments at, among other institutions, Princeton University, the University of Michigan, and the University of Hawaii at Manoa ...”

This book is now in at least its 15th edition, which may explain why the number of fallacies has changed. Over time, the author/editors probably combined certain fallacies into one fallacy.

FYI, there are affordable, used editions of this book online that sell for under $10. I’m going to grab a third edition that looks to be in pretty good shape for $25. Thanks for the tip. I love interesting old books!

answered on Friday, Feb 26, 2021 08:36:16 AM by Jordan Pine

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David Blomstrom writes:

Thanks for the tip. Unfortunately, I seldom buy paperback/hardback books. I just love the convenience of epubs.

But I would love to have an epub version of Copi's book on my laptop.

Note, however, that Copi's book may have fallen out of favor. Do some research on "Hamblin." I think he's the guy who subjected it to some pretty heavy criticism and helped steer the study of fallacy in a new direction. However, I'm not sure if there's a current fallacy "Bible."

 

posted on Friday, Feb 26, 2021 08:51:59 AM
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Jordan Pine writes:
[To WebRanger]

This appears to be an eBook of the latest edition:

https://www.anhshops.com/products/ebook-pdf-introduction-to-logic-14th-edition-by-irving-m-copi

[ login to reply ] posted on Friday, Feb 26, 2021 10:10:57 AM
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David Blomstrom writes:
[To Jordan Pine]

Good find; thanks.

[ login to reply ] posted on Friday, Feb 26, 2021 10:12:46 AM
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David Blomstrom writes:

Charles Leonard Hamblin. A hardcover version of his book is available for almost $800. ;)

https://www.amazon.com/Fallacies-No-C-L-Hamblin/dp/0916475247

posted on Friday, Feb 26, 2021 08:55:03 AM
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Jordan Pine writes:
[To WebRanger]

Thanks for this tip as well! I ordered it from the Marketplace for $40.

[ login to reply ] posted on Friday, Feb 26, 2021 10:16:25 AM