False Logical Fallacies

Republished versions of old posts have proven quite popular with my readers, so here's another one from the vaults. OP date 8/20/2014. Discuss:

To someone with formal training in logic, the internet can be a strange place indeed. It's analogous to being a pharmacist at an Old West medicine show. People guzzle down snake oil and keep going back for more.

One of the major reasons for these continued errors is many commentators' habit of parroting phrases they've seen online without taking the time to really understand what these concepts mean. As a public service, I'll cover a few of the more commonly misunderstood ideas, including often distorted logical fallacies.

Let's start by defining what "argument" means. Contrary to popular misuse, arguing doesn't mean verbally attacking someone or browbeating a debate opponent into shutting up. An argument is just two or more people trying to reach the truth through dialogue--trading premises back and forth.

Since this post is primarily concerned with logical fallacies and the misidentification thereof, we need to talk about syllogisms--the category of arguments that logical fallacies apply to. A syllogism is a form of deductive argument constructed from two or more premises leading to a conclusion that, if the premises are true and the form is correct, must also be true.

Syllogism Example:
A) All popes are Catholic.
B) Jorge Mario Bergoglio is the Pope.
Therefore, Jorge Mario Bergoglio is Catholic.

The picture of Chewbacca fighting Nazis while riding a giant squirrel illustrates two important points. The first is the need to define logical invalidity. There's a widespread misconception that "invalid" means "untrue". That's not necessarily the case. A syllogism is valid if its conclusion follows from the premises, even if the premises and/or conclusion are completely false. Therefore, validity only refers to an argument's form; not its truth value.

Here's a false yet valid argument:
A) Everything that's brown is a bear.
B) My car is brown.
Therefore, my car is a bear.

The conclusion is false because premise A is false; not because the syllogism is structured improperly. The false conclusion does follow from the premises.

Got it? Doesn't matter. I'll discuss some fake logical fallacies anyway.

1. Godwin's Law
The Chewie picture's second lesson. Godwin's Law predicts that the likelihood of Hitler/Nazis being invoked in an internet argument is directly proportional to the duration/intensity of said argument. Comparing someone to Hitler in a combox is hyperbolic and cliched, but it's not necessarily fallacious. The following valid argument shows why:

A) An evil act is evil regardless of who the perpetrator is.
B) Hitler committed genocide.
C) Hitler's genocide was evil.
D) Stalin also committed genocide.
Therefore, Stalin's genocide was evil.

So you can say that anyone who brings up Nazis forfeits the debate, but doing so is a rhetorical--not a dialectical--move.

2. No True Scotsman
No True Scotsman is a rhetorical device that isn't formally fallacious (only informally). It's not a structural flaw in an argument, but an attempt to dodge an unwanted conclusion.

Jack: No writers are Libertarians.
Bob: I'm a writer, and I'm a Libertarian.
Jack: Well, no real writers are Libertarians.

On the other hand, No True Scotsman arguments can still be valid.
A) Everything that flies is a bird.
B) Bats fly.
C)Therefore, bats are birds.
D) But all true birds have feathers.
E) Bats don't have feathers.
F) Therefore, bats aren't birds.

3. Reductio ad infinitum
One effective way to disprove an argument is to show that it necessarily leads to an absurd conclusion. An argument that concludes to an infinite regress is one such absurdity. Nevertheless, the web abounds with claims that Reductio ad infinitum is a logical fallacy.

The reason that some folks call shenanigans on this type of reductio argument is because Aristotle and Aquinas use it in their proofs for God. As Dr. Edward Feser definitively shows, the same people who dismiss Reductio ad infinitum as fallacious commit the very real Straw Man fallacy in the process.

The confusion seems to arise from Bertrand Russell cribbing David Hume's incomplete treatment of classical First Cause arguments. Their Straw Man refutation goes like this: "If everything has a cause, and God caused the universe, what caused God?"

Russell's counter-argument would be valid if it addressed what Aristotle, Aquinas, et al. actually said. Neither the Aristotelians nor the Scholastics ever claimed that "Everything has a cause." That canard is a gross simplification of sophisticated arguments that are really more like, "Everything that exists contingently must receive its being from something that exists necessarily." The accusation of special pleading leveled at the straw man utterly fails against the original argument.

As for why an infinite regress is absurd, Consider a train so long as to circle the equator that's all boxcars with no engine. Is the idea of those cars going anywhere on their own rational? Exactly.

So ends the post. Hopefully it has gone a short way toward elevating the state of online discourse. If you can think of any more non-fallacies, leave a comment below. I may do other posts on this topic.


  1. As I commented on the original one recently: Slippery Slope!

    Look at the pro-homosexual judicial and legislative agenda since at least the '90s, where at every step people against them said the current state of affairs is where things would end. Everyone on the homosexual side denied it, perhaps honestly (with others in the wings wanting to take things further than perhaps these people wanted), or dishonestly (they wanted more, but didn't want to admit it).

    1. The progressive ailment called 'gun control' works the same way.

    2. "The progressive ailment called 'gun control' works the same way."

      See Eric S. Raymond about that at The progressive ailment called 'gun control' works the same way.

      I suspect abortion did as well, but I wasn't alive then and so didn't experience it.

    3. I was going to rant about 'Slippery Slope', but you beat me to it. I lost track of how many times I heard that 'arguing that normalizing homosexual relationships with normalize pedophilia, polygamy, bestiality and necrophilia is a Slippery Slope fallacy!' And since then there is serious talk about removing laws forbidding plural marriage and the 'polyamory' craze has boomed. I will not get started on the evil of the 'MAP' movement, but every single once of those things has either happed or gained headway.

      (And loli fans, but the slippery slope being real, and being a cliff does not bode well for your arguments either.)

    4. Concur. It's not fallacious if you've seen it happen.

    5. DJ - I agree. ESR's survey of the futility of compromise just about knocks it about of the park on this subject.
      LawDog's Cake Analogy also illustrates it very well.

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  3. I'll admit my training with Logic was limited to a class that involved truth tables, and some quasi calculus thing in the latter half of the class.

  4. Does anyone have a case where conservatives/traditionalists/the right called something a Slippery Slope and turned out to be WRONG?

    It's kind of crazy that "philosophers" would start their argument for materialism by casually discarding causality, thus rendering materialism itself meaningless.

    I believe the correct form is "the potential only becomes actual when acted on by the already actual". Even a probabilistic relationship can be actual, as per quantum physics.

    1. They haven't been wrong about any of it. That is one of the reasons so many moderates and liberals have shifted (even slightly) right over the last decade. Only Lemmings, or the insane, willingly run off a cliff they can clearly see ahead.