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Informal Fallacies: 11 Argumentative Errors Worth Knowing and Avoiding

Ladies and gentlemen of this supposed jury, it does not make sense! If Chewbacca lives on Endor, you must acquit! The defense rests.

Chewbacca Defense, South Park

When it comes to appearance over substance, the Chewbacca Defense could easily be the mothership of all fallacies. The goal of this legal strategy is to win the argument by distracting and confusing everyone involved to such an extent that they simply agree with the presented conclusion. To achieve this, the speaker launches into an elaborate nonsense argument packed with formal and informal fallacies.

A formal fallacy entails fundamental mistakes in structure and logic. The premise may be true but the conclusion is invalid. An informal fallacy, on the other hand, is an error in an argument’s content or context. This extends to irrelevance, ambiguities or misleading assumptions. Such arguments appear sensible on the surface but fall apart on closer inspection. Here are a selected few informal fallacies. Eleven examples worth knowing and avoiding.

1. No True Scotsman

Bob: All Scotsmen prefer scotch over gin.

Sara: But my brother is a Scotsman and he likes gin better.

Bob: Right, seems like your brother isn’t a true Scotsman.

A vast generalisation is usually the starting point for the No True Scotsman Fallacy. However, the broader the statement the easier it is to refute it with a simple counter-example. Well done there, Sara. By invoking her Scottish brother, Sara falsifies Bob’s argument. With his argument technically falsified, Bob now resorts to an ‘appeal to purity’.

It’s an attempt to strip Sara’s brother of his Scottishness for Bob’s personal gain, a last-ditch effort to save his generalisation from falling apart. Bob retroactively invokes a vague, rather emotional and subjective criterion of authenticity. Conveniently, this isn’t a bar Sara’s brother can pass as long as Bob doesn’t want him to.

As philosopher Antony Flew has pointed out, the No True Scotsman Fallacy is often used to protect a group from the unfavourable acts of one of its members. As in: ‘No, Bob’s not one of us. No true philosopher would ever make an appeal to purity.’

2. Argument from Anecdote

Bob: A friend of mine has been skydiving for 10 years and he’s never had an accident. So it can’t be dangerous.

Perhaps one of the most common informal fallacies is the Argument from Anecdote, which uses a personal account as evidence for a claim. Bob here tries to pass his own experience for an argument. We can assume that Bob is sincere in his observation and didn’t just make it up. But there’s really not much room to verify his claim.

The argument from anecdote is a form of generalisation. Even if Bob speaks the truth, it doesn’t give us any statistically meaningful data about the actual dangers of skydiving. We may view Bob’s argument as obviously poor and we may mock Bob for being overly simplistic. Until the next time when we catch ourselves mistaking a personal anecdote for a universally true argument.

3. Tu Quoque

Sara: You said lying is wrong and bad for your karma. But then you lied about liking scotch over gin. So you were wrong all along, Bob.

Tu Quoque is another one of those righteous informal fallacies. The expression is Latin for ‘you also’. It happens when we argue that a speaker’s actions do not align with his or her words and therefore discount what they said. Sara is probably right to take Bob’s advice with a grain of salt. In fact, Bob may very well be a hypocrite. While it may affect his karma, it doesn’t necessarily invalidate his original point.

This is why the Tu Quoque Fallacy is a special form of ad hominem, an attack against the speaker as a person. I guess that’s where the saying ‘Do as I say and not as I do,’ comes from. It’s an acknowledgement of an unfortunate tendency: Occasionally, people fail to live up to their own expectations. A better strategy is to not let those failings interfere with coming to our own conclusions.

4. Trivial Objections

Bob: It’s impossible for Australia to be a continent. It’s only a single country.

Sara: It can be a single country and still be a continent.

Bob: Okay, but it’s an island.

Those who employ Trivial Objections hit a speaker with a barrage of irrelevant complaints and technicalities in order to avoid addressing an argument. It’s a form of deception, a red herring designed to distract from the issue at hand by ignoring the main claim.

Most likely, Bob knows he’s lost the argument. Instead of conceding, he opposes Sara’s position with objections irrelevant to the question. Chances are it will take Sara a while until she realises Bob is not arguing in good faith. Let’s hope he doesn’t resort to the most desperate of all red herrings, the Dead Cat Manoeuvre.

5. Is-Ought Fallacy

Sara: Things have always been like that. So why would we want to make any changes?

To understand the Is-Ought Fallacy we first have to make an important distinction: What is and what should be are two entirely different things. Arguing that something is a certain way, doesn’t mean we condone or even support it. However, the error with this fallacy is to argue that something should be a certain way because things are a certain way. Sara here “asserts that the status quo should be maintained simply for its own sake”[2].

6. Ought-Is Fallacy

Bob: This is the best example for the Ought Is fallacy. It has to be. I can’t think of another one.

The Ought-Is Fallacy represents the other side of the Is-Ought coin. It’s all about arguing that something is a certain way because that’s what we want it to be. Bob makes the case for his example not because it’s true. It’s more a case of wishful thinking and motivated misperception. Trying to bend reality to suit your argumentative needs is not cool, Bob.

As illustrated by the Dead Horse Theory, this kind of informal fallacy seems to be common in bureaucratic institutions. The Dead Horse Theory suggests that organisations will do anything to avoid recognising that the metaphorical horse they’re riding has long been deceased.

7. Pooh-Pooh Fallacy

You can’t be serious, man. You cannot be serious!

John McEnroe

Committing a Pooh-Pooh is “to dismiss an argument with ridicule as not worthy of serious consideration”[1]. Of course, the example above is taken from John McEnroe’s famous outbreak at Wimbledon in 1981. After the umpire determines that his serve was out, he utters the immortal words that dismiss the official’s claims out of hand.

Pooh-poohing (presumably originating from an expression of disgust) is similar to strawmanning, which happens when an argument is misrepresented to make it easier to attack. In McEnroe’s defence, he followed up with a more substantial point: “That ball was on the line. Chalk flew up. It was clearly in.”

8. False Dichotomy

Bob: McEnroe was right. The ball was either well in or clearly on the line. What do you think, Sara?

The False Dichotomy is a sneaky informal fallacy. It happens when a speaker presents two options and two options only as potential explanations. But there’s one caveat. The choice presented has to be unfair, as is the case in Bob’s little speech. This informal fallacy tends to have only one effective solution: rejecting the premise of the argument entirely.

What Sara’s going to do next is to challenge Bob’s scenario of only two plausible options. John doesn’t like to hear it but the ball could’ve also been out. Obviously. As a linguistic trick it’s similar to Morton’s Fork, a sneaky decision-dilemma I wrote about in 7+1 Paradoxical Examples of Mind-Bending Contradictions.

9. Appeal to False Authority

Sara: Absolutely, the ball was out. Just ask Bob, he‘s the expert on outdoor furniture.

The Appeal to False Authority is quite self-explanatory. It’s generally fine to refer to an authority figure in our reasoning. After all, true experts tend to be at the boundary of the known and the unknown. However, Sara is invoking Bob as an authority on a subject that’s clearly irrelevant to the debate.

We should note, though: Even if Bob was a tennis expert that wouldn’t necessarily make Sara’s argument true. There’s usually more than one authority in any given field and they have the good habit of disagreeing. Trustworthiness and the accuracy of expert quotes are other points to look out for when an appeal to authority is made.

10. Begging the Question

Bob: The ball was clearly out because it wasn’t in.

Begging the Question, also known as petitio principii, is a form of futile circular reasoning and similar to a meaningless tautology. This informal fallacy leaves the audience wondering because the arguer hasn’t actually answered the question or provided any supporting evidence for their claim.

As opposed to McEnroe, Bob tries to get around the pesky evidence part when arguing whether the ball was in or out. In reality, Bob doesn‘t get us closer to a real answer, he just assumes that his conclusion is true. Informal fallacies from this category are reminiscent of linguistic oddities, expressions you have to think about long and hard to make sense of them.

11. Argument from Ignorance

Somebody sees lights flashing in the sky. They never seen it before. They don’t understand what it is. They say: “A UFO!” The ‘U’ stands for unidentified. So they say: “I don’t know what it is. It must be aliens from outer space visiting from another planet.”

Neil deGrasse Tyson

People making this error in informal logic assume the truth or falsity about a claim because of the mere fact that there is no evidence to the contrary. Admittedly, Neil’s example of such an appeal to ignorance is rather implicit. His UFO spotter presupposes the UFO is alien in view of the fact that there is no evidence.

More broadly, as the astrophysicist explains, when falling for the Argument from Ignorance we tend to “go from an abject statement of ignorance to an abject statement of certainty.” We should cut ourselves some slack, though. We seem to be prone to do it as an initial and intuitive assessment of a situation; as a mental shortcut so to speak. We should, however, give the argumentum ad ignorantiam a miss when we have the time to carefully consider what we’re about to say.

BONUS: Irrelevant Conclusion

Bob: This list of informal fallacies is pretty good.

Sara: Ha! That just proves that they can easily be avoided.

An Irrelevant Conclusion is fallacious simply because it misses the point. Bob here was making a remark about the quality of our list. He may or may not be correct. However, his observation is not relevant to the question of whether we can easily steer clear of informal fallacies. Put differently, Sara’s conclusion doesn’t address the question.

Closing Thoughts

There’s a myriad of informal fallacies out there. You’d have to be very present and quick-witted to avoid them all and all the time. A more positive approach would be to study Graham’s Hierarchy of Disagreement. It’s a great way to avoid many of the pitfalls of reasoning by learning how to disagree on an expert level.

As opposed to Bob, I won’t lie. It’s surely easier, more intuitive and perhaps more fun to mount a fallacy-ridden Chewbacca Defense than crafting a sound argument. But if we prefer to put in the hard work needed to find the truth we should avoid the potential for manipulation and superficiality that comes with informal fallacies.