English

logical_fallacies.pptx

Logical Fallacies

14 April 2016

Quick Review of Logic Basics

Logic is the study of arguments, a formal system of analysis that helps writers invent, demonstrate, and prove arguments.

Inductive reasoning moves from a specific premise to a general conclusion by gathering observations (premises) and then drawing a conclusion.

Deductive reasoning moves from a general premise to a more specific conclusion by testing premises against each other and coming to the only logical conclusion available.

What are logical fallacies?

Fallacies are common errors in reasoning that will undermine the logic of your argument. Fallacies can be either illegitimate arguments or irrelevant points, and are often identified because they lack the evidence necessary to support their claim.

There are two types of fallacies:

Formal fallacies (deductive fallacies)

Informal fallacies (inductive fallacies)

Two Types of Fallacies

Deductive/Formal Fallacies

Deductive arguments are supposed to be water-tight. For a deductive argument to be a good one, it must be absolutely impossible for both of its premises to be true and its conclusion to be false. With a good deductive argument, that simply cannot happen.

Inductive/Informal Fallacies

Inductive arguments aren’t as rigorous as deductive arguments. Good inductive arguments lend support to their conclusions, but even if their premises are true, it doesn’t necessarily mean that their conclusions are true. Even if both premises are true, the conclusion might be false.

Inductive/Informal Fallacies

Common Types of Fallacies

As illustrated by Kenna, her family, her friends, and some crappy politicians

Strawman

Misrepresentation of someone’s argument to make it easier for you to attack

By exaggerating, misrepresenting, or just completely fabricating someone’s argument, you make it easier to present your own position as being reasonable, but this kind of dishonesty undermines rational debate

Kenna: We should probably spend more of our tax money on healthcare and education if we want to keep up with the changing global economy.

Mom: I’m surprised you hate our country so much that you want to leave it defenseless by cutting military spending.

False Cause

Presumes that a real of perceived relationship between things means that one is the cause of the other

Many people confuse correlation (things that happen together or in sequence) for causation (that one thing actually causes the other to happen). Sometimes correlation is coincidental, or it may be attributable to a common cause.

Kenna: As you can see from my fancy chart, environmental temperatures have been rising over the past few centuries, whilst at the same time, the numbers of pirates have been declining. It’s obvious what we have to do. Save the pirates, save the planet.

Appeal to Emotion

Attempt to manipulate an emotional response in place of a valid or compelling argument

Appeals to emotion include appeals to fear, envy, hatred, pity, pride, and more. It’s important to note that sometimes a logically coherent argument may inspire emotion or have an emotional aspect, but the problem and fallacy occurs when emotion is used instead of a logical argument, or to obscure the fact that no compelling rational reason exists for your position. Everyone, except sociopaths, is affected by emotion, and so appeals to emotion are a very common and effective argument tactic, but they’re ultimately flawed, dishonest, and tend to make your opponents justifiably emotional.

Kenna: I don’t want to eat sheep brains with chopped liver for dinner! I’m a vegetarian!

Dad: Think about the poor, starving children in a third world country who aren’t fortunate enough to have any food at all. They’re all starving to death while you sit there with your nose turned up, scoffing at the food that could save them from their untimely demise!

Kenna: *tears*

Kenna: *chews*

Kenna: *sobs*

Fallacy Fallacy

Presumption that because a claim has been poorly argued, or a fallacy has been made, that the claim itself must be wrong.

It is entirely possible to make a claim that is false yet argue with logical coherency for that claim, just as it is possible to make a claim that is true and justify it with various fallacies and poor arguments.

Kenna: If we allow Donald Trump to be President, we’re telling the world that even an orangutan in a toupee is qualified to run the free world! We have to vote responsibly!

Mom: That’s such a gross exaggeration! If we elect Donald Trump, freeloading liberal hippies like you won’t be able to screw up our government!

Slippery Slope

If we allow A to happen, then Z will eventually happen too, therefore A should not happen.

The problem with this reasoning is that it avoids engaging with the issue at hand, and instead shifts attention to extreme hypotheticals. Because no proof is presented to show that such extreme hypotheticals will in fact occur, this fallacy has the form of an appeal to emotion fallacy by leveraging fear. In effect, the argument at hand is unfairly tainted by unsubstantiated conjecture.

Cousin Joe: If we let same-sex couples marry each other, then the next thing we know we’ll be allowing people to marry their parents, their cars – heck! – even their pets!

Kenna: There is no way we are biologically related…

Ad Hominem

Attacking opponent’s character or personal traits in an attempt to undermine their argument.

Ad hominem attacks can take the form of overtly attacking somebody or more subtly casting doubt on their character or personal attributes as a way to discredit their argument. The result of an ad hom attack can be to undermine someone’s case without actually having to engage it.

Kenna: This year’s tax brackets dictate that teacher’s who can barely get by on $40,000 a year have to pay the same 25% tax rate as the president of a university who made almost $100,000 dollars last year and who owns a vacation house in Florida. If we shift our tax brackets even just 2% to increase taxes on the rich, we can stimulate the economy and help the lower-middle class avoid poverty.

Donald Trump: Can we really take Kenna seriously? I mean, she’s covered in tattoos and she looks like the sort of person who’d steal cheap makeup from Walmart.

Tu Quoque

Avoiding having to engage with criticism by turning it back on the accuser – answering criticism with criticism

Pronounced too-kwo-kwee. Literally translating as “you too,” this fallacy is also known as the appeal to hypocrisy. It is commonly employed as an effective red herring because it takes the heat off of someone having to defend their argument, and instead shifts the focus back on to the person making the criticism.

Kenna: You have received a C on your research paper because you didn’t successfully defend your argument and because all of your sources come from Fox News.

Angry Student: Yeah, well, obviously you didn’t teach me how to do research properly! That’s why all of your students hate this class!

Personal Incredulity

Because you found something difficult to understand, or are unaware of how it works, you suggested that the claim is probably false.

Complex subjects like evolution through natural selection require some amount of understanding before you are able to make an informed judgment about the subject at hand; this fallacy is usually used in place of that understanding.

David: *draws a stick figure and a fish next to each other*

David: *scoffs with disdain*

David: Do you really believe we’re stupid enough to believe that a fish somehow turned into a human through just, like, random things happening over time??

Kenna: *face palm*

Special Pleading

Moving the goalposts or making up an exception when your claim was shown to be false.

Humans are funny creatures and have a foolish aversion to being wrong. Rather than appreciate the benefits of being able to change one’s mind through better understanding, many will invent ways to cling to old beliefs. One of the most common ways that people do this is to post-rationalize a reason why what they thought to be true must remain true. It’s usually very easy to find a reason to believe something that suits us, and it requires integrity and genuine honesty with ourselves to examine our own beliefs and motivations without falling into the trap of justifying our existing ways of seeing ourselves and the world around us.

Aunt Dorris: I have always had the gift to read minds.

Kenna: Really? What am I thinking of right now?

Aunt Dorris: Hmm… You’re thinking about... what you’re going to have for dinner.

Kenna: Actually, I was thinking about the inevitable heat death of the universe.

Aunt Dorris: That’s your problem! You have to have faith in my abilities for them to work!

Loaded Question

Asking a loaded question that had a presumption built into it so that it couldn’t be answered without appearing guilty.

Loaded question fallacies are particularly effective at derailing rational debates because of their inflammatory nature – the recipient of the loaded question is compelled to defend themselves and may appear flustered.

Kenna: I’ll be voting liberal this election because social justice is my number one concern. There aren’t any conservative politicians running this year who seem to believe social justice and equality are important.

Cousin Dan: Do you know that your political views are destructive to American integrity?

Kenna:

Burden of Proof

Saying that the burden of proof lies not with the person making the claim, but with someone else entirely

The burden of proof lies with whomever is making a claim, and is not the responsibility of anyone else to disprove. The inability, or disinclination to disprove a claim does not render that claim valid, nor give it any credence whatsoever. However it is important to note that we can never be certain of anything, and so we must assign value to any claim based on the available evidence, and dismiss something on the basis that it hasn’t been proven beyond all doubt is also fallacious reasoning.

Kenna: There is, at this very moment, a teapot in orbit around the Sun, between Earth and Mars.

Alex: Kenna, that’s ridiculous.

Kenna: Prove I’m wrong then!

Ambiguity

Use of a double meaning or ambiguity of language to mislead or misrepresent the truth

Politicians are often guilty of using ambiguity to mislead and will later point to how they were technically not outright lying

Judge: Young lady, why haven’t you paid your parking fine?

Kenna: I shouldn’t have to pay them!

Judge: Why not? The sign clearly said, “Fine for parking here.”

Kenna: Yeah, so it should have been fine to park there!

Gambler’s Fallacy

Saying that “runs” occur to statistically independent phenomena such as roulette wheel spins

This commonly believed fallacy can be said to have helped create an entire city in the desert of Nevada. Though the overall odds of a “big run” happening may be low, each spin of the wheel is itself entirely independent from the last. So whilst there may be a very small chance that heads will come up 20 times in a row if you flip a coin, the chances of heads coming up on each individual flip remain 50/50, and aren’t influenced by what happened before.

Kenna: *playing roulette*

Kenna: Alright, it’s been red six times in a row, so black should be up next. I’ll put it all on black!

Dealer: Um… That’s not how it works...

Kenna: DO IT, CASINO SLAVE!

*wheel turns*

Dealer: Red 16. Sorry, lady.

Kenna: *tears*

Bandwagon

Appeal to popularity or the fact that many people do something as an attempted form of validation.

The flaw in this argument is that the popularity of an idea has absolutely no bearing on its validity. If it did, then the Earth would have made itself flat for most of history to accommodate this popular belief.

Alex: *points finger drunkenly at Kenna*

Alex: How can leprechauns only be a superstition if so many people – hiccup – if so many people believe in them??

Kenna: *finishes beer*

Kenna: *falls off chair*

Appeal to Authority

Saying that because an authority thinks something, it must be true

It’s important to note that this fallacy should not be used to dismiss the claims of experts, or scientific census. Appeals to authority are not valid arguments, but nor is it reasonable to disregard the claims of experts who have demonstrated depth of knowledge unless one has a similar level of understanding and/or access to empirical evidence. However, it is entirely possible that the opinion of a person or institution of authority is wrong; therefore the authority that such a person or institution holds does not have any intrinsic bearing upon whether their claims are true or not.

Cousin Laura: Evolution is a bunch of malarkey!

Kenna: But all of the credible scientific evidence of the past century suggests –

Cousin Laura: I saw an article in the New York Times by a doctor in Arkansas who says evolution was made up by Darwin to convert people to Satanism!

Kenna: I can’t even with you right now…

Composition/Decomposition

Assumption that one part of something has to be applied to all, or other, parts of it; or that the whole must apply to its parts.

Often when something is true for the part it does also apply to the whole, or vice versa, but the crucial difference is whether there exists good evidence to show that this is the case. Because we observe consistencies in things, our thinking can become biased so that we presume consistency to exist where it does not.

Bill Nye: Everything is made up of atoms, and atoms are invisible to the naked eye.

Student: Well, that must mean…

Student: *arrives at class naked*

Kenna: Mother Mary on a pogo stick! What is wrong with you!?!?

Student: Shh... I’m invisible...

No True Scotsman

Appeal to purity as a way to dismiss relevant criticisms or flaws of your argument

In this form of faulty reasoning one’s belief is rendered unfalsifiable because no matter how compelling the evidence is, one simply shifts the goalposts so that it wouldn’t apply to a supposedly “true” example. This kind of post-rationalization is a way of avoiding valid criticisms of one’s argument.

Chloe: No true feminist shaves her legs!

Kenna: I’m a feminist. I’ve devoted my entire life to equal rights for people of all gender identities. And I definitely shave my legs.

Chloe: Misogynist pig!

Genetic Fallacy

Judgment of something as either good or bad on the basis of where it comes from, or from whom it came

This fallacy avoids the argument by shifting focus onto something’s or someone’s origins. It’s similar to an ad hominem fallacy in that it leverages existing negative perceptions to make someone’s argument look bad, without actually presenting a case for why the argument itself lacks merit.

Kenna: Senator, I saw I story on the news last night that you’ve been taking bribes on Capitol Hill from lobbyists. How can I trust that you have the constituents’ best interests in mind if your loyalty can be bought and sold like that?

Sen.: I expected better from you, Kenna. You should be very wary of the things you hear in media, because we all know how unreliable the media can be.

Sen.: *stuffs blood money in pocket*

Sen.: *shifty eyes*

Black or White Fallacy

Presenting two alternatives as the only possibilities, when in fact more possibilities exist.

Also known as the false dilemma, this insidious tactic has the appearance of forming a logical argument, but under closer scrutiny it becomes evident that there are more possibilities than the either/or choice that is presented. Binary, black-or-white thinking doesn’t allow for the many different variables, conditions, and contexts in which there would exist more than just the two possibilities put forth. It frames the argument misleadingly and obscures rational, honest debate.

Kenna: I’m sorry. I love you, but you know I can’t write this paper for you. That would be plagiarism.

Emma: You can either help me succeed, or you can force me to fail out of graduate school!

Kenna: Or you could just do your own–

Emma: It’s ride or die, b*tch.

Kenna: But –

Emma: RIDE OR DIE.

Begging the Question

Presenting a circular argument in which the conclusion was included in the premise

This logically incoherent argument often arises in situations where people have an assumption that is very ingrained, and that assumption is therefore taken in their minds as a given. Circular reasoning is bad mostly because it’s not very good.

David: I was raised as a Zorbian my whole life, so I know Zorbo created Earth and placed us here to glorify his name and harvest souls for the Eternal Continuum.

Kenna: What in the – ?

Kenna: David, why? Just why?

David: Look, it says so right here in the Great and Infallible Book of Zorbo’s Best and Most Truest Things that are Definitely True and Should Not Ever Be Questioned.

Appeal to Nature

Arguing that just because something is “natural” it is therefore valid, justified, inevitable, good, or ideal.

Many “natural” things are also considered “good,” and this can bias our thinking; but naturalness itself doesn’t make something good or bad. For instance, murder could be seen as very natural (because it happens so often), but that doesn’t mean it’s good or justifiable.

Kenna: I have a horrible headache...

Chloe: Here, drink this mud water! It’s harvested organically from the Appalachian Mountains.

Kenna: Yeah, no... I’m just going to take some Advil and lay down.

Chloe: *slaps bottle out of Kenna’s hand*

Chloe: Don’t take that! It’s basically poison! Look, there isn’t one natural ingredient in the entire ingredients list!

Kenna: Girl, you need science...

Anecdotal

Using a personal experience or an isolated example instead of a sound argument or compelling evidence.

It’s often much easier for people to believe someone’s testimony as opposed to understanding complex data and variation across a continuum. Quantitative scientific measures are almost always more accurate than personal perceptions and experiences, but our inclination is to believe that which is tangible to us, and/or the word of someone we trust over a more abstract statistical reality.

Jason: *glug*

Kenna: Dude, are you drinking straight up melted butter right now? That really isn’t good for you. Butter is full of saturated fats that can cause heart disease, obesity, colon cancer –

Jason: I call BS. My grampa used to drink like, a gallon of ranch dressing a year, and he lived until he was 97, so I think you need to check yo’ self before you wreck yo’ self.

Kenna:

The Texas Sharpshooter

Cherry-picking a data cluster to suit your argument, or finding a pattern to fit a presumption

This “false cause” fallacy is coined after a marksman shooting randomly at barns and then painting bullseye targets around the spot where the most bullet holes appear, making it appear as if he’s a really good shot. Clusters naturally appear by chance, but don’t necessarily indicate there is a causal relationship.

Kenna: It’s extremely unethical that you market your Sugarette Candy Drinks soley to children when American children are facing an obesity crisis.

Spokesperson: Our research shows that of the five countries where Sugarette drinks sell the most units, three of them are in the top ten healthiest countries on the planet for people to live in, so Sugarette can’t be all that bad for you.

Kenna: *looks at chart*

Kenna: Two of these countries are remote islands inhabited solely by monkeys, and the third is Antarctica.

Spokesperson: The research doesn’t lie.

Middle Ground

Claiming that a compromise, or middle point, between two extremes must be the truth.

Much of the time the truth does indeed lie between two extreme points, but this can bias our thinking; sometimes a thing is simply untrue and a compromise of it is also untrue. Half way between truth and a lie is still a lie.

David: A study in 2009 showed that vaccinations are responsible for autism in children. We have to stop vaccinating our kids if we want to avoid ruining our children’s lives!

Kenna: Autism isn’t fatal, but measles is. Regardless, there have been literally hundreds of studies that have completely debunked that theory since then.

Chloe: Guys, guys, let’s not fight. Can’t we come to a compromise? Maybe vaccinations cause some autism, just not all autism.

Kenna: You are both fired from my squad.