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An Introduction to Logical Fallacies for the Curious RFer

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Sunstone

De Diablo Del Fora
Premium Member
I have long been of the opinion that the main reason to study logic is to avoid being duped. I know some people study logic so that they can "win" debates -- whatever "winning" might mean to them -- but I myself don't believe that's much of a reason to study logic.

It's been my experience that very few people, if any, change their minds on merely logical grounds. In the first place, most of us humans are very stubborn when it comes to changing our minds. In the second place, when we do change our minds, we usually do so for reasons having little to do with logic, and much more to do with emotion, self-interest, and egotism.

So, for me, the best reason to study logic is to avoid being duped. Either duped by someone else or -- more likely -- duped by oneself. For we humans fool ourselves much more often than we fool others.

The Nature and Purpose of Logic

It is possible to define "reasoning" as a highly specialized form of thinking that primarily involves the conscious recognition of cause and effect relationships. If that's how we define reasoning, then "logic" can be defined as the systemic study of the standards (or rules) of good reasoning.

For instance, suppose we reveal to our cousin that we were are an RFer. She faints. At that point, we might reason the cause of her fainting was our revelation. But do we have good grounds to believe that it was? This is when logic comes in. Logic is a way of figuring out how well we are reasoning.

Sometimes cause and effect relationships are easy to recognize, and it doesn't take much reasoning to see them. But sometimes they are more difficult to recognize, and we need to do a lot of reasoning to see them. The more reasoning we need to do to see or recognize a cause and effect relationship, the more that logic can help us to reason well.

The Dawn of Logic

People have always reasoned, and they have always now and then reasoned logically, but they have not always systemically studied logical reasoning. In the West, the study of logical reasoning didn't get underway until about 2,300 years ago. I don't know whether it began any earlier elsewhere, but that's when it began in the West -- and it for the most part began with just one man. Aristotle.

Aristotle lived in Athens, Greece, where he wrote five books on the subject of logic. Together, the books are called the Organon, which can be roughly translated as "The Tools of Thought". Most of what he wrote about logic is still considered correct even today.

Perhaps the single most curious thing about Aristotle was his creative brilliance. Most of the great minds of history have built on the work of people who came before them. For instance, in the case of mechanics, Newton drew from the work of Descartes, Galileo, and Kepler. But Aristotle pretty much created the study of logic all by himself.

A Couple Other Things...

I will be adding to the thread as time permits, but it will never be a comprehensive account of every fallacy on the books. I plan instead to focus on what I believe are the most common fallacies -- in no particular order.

Last, this thread is closed, but if you have any questions or concerns about it, please feel free to PM me.
 

Sunstone

De Diablo Del Fora
Premium Member
What on Earth is a Logical Fallacy?

For the purposes of this thread, I am defining "logical fallacy" as "an argument that appears to be correct, but which proves, upon examination, not to be so".

That is (largely) how Irving Copi defined the term in the first edition of his influential textbook, Introduction to Logic (1961). Naturally, his definition is controversial. Lots of logicians have criticized it -- and sometimes rightfully so. But I find Copi's definition -- as modified by me -- adequate to our needs here.

Broken down, his definition has two key parts (in my opinion):

1) Argument. In logic, an "argument" is NOT the same as a debate or disagreement between people. Instead, it is a chain of premises intended to lead to a conclusion. Whether anyone agrees or disagrees with an argument is irrelevant to whether or not something is an argument -- at least, in logic.

2) Correctness. This is a broad term that allows for deductive invalidity, inductive weakness, and some other ways arguments can fail.
Please note that intention has nothing to do with whether or not something is a fallacy. If a bit of reasoning is erroneous, it's erroneous regardless of whether or not it was intended to be erroneous. Logic is impersonal -- it has nothing to do with intentions or a lack of them.
 

Sunstone

De Diablo Del Fora
Premium Member
The noble and esteemed AD HOMINEM or PERSONAL ATTACK fallacy
Many of us are in the habit of calling any and all personal attacks "ad hominem fallacies". As it happens, that is not true -- at least not true in logic. Some personal attacks are illogical, some are logical, and some have nothing to do with logic at all.

If you simply call someone a "Perkle-Squatting Snerple-Dick" -- without any reference at all to a statement or an argument they've made -- that is a personal attack that has nothing to do with logic. For a personal attack to be a genuine ad hominem, it must first of all seek to undermine a statement or an argument. Just calling someone a name is not a true (i.e. fallacious) ad hominem.

So what makes an ad hominem a fallacy?

The principle involved is this: The ad hominem or personal attack is a fallacy when it is irrelevant to whether or not a statement or an argument is a good one. If and when a personal attack is actually relevant to whether or not a statement or an argument is a good one, the personal attack is not a fallacy.

For example, consider this typical RF exchange:

@Terese: My dogs only bark at strangers, so it's quite obvious that they are capable of recognizing someone they've seen before.

@SalixIncendium: Even though your dogs only bark at strangers, you, my dear, are a Leprecous Turkle-Breathing Spost-Flinger and thus your dogs are actually incapable of recognizing someone they've seen before.

@Terese: Nuh-uh.​

Salix is committing an ad hominem here because his personal attack on Terese is irrelevant to whether or not Terese's conclusion is true or false. Tut! Tut!

But what about this case:

PETER "LYING PETE" BOARDMAN: The District Attorney's investigation of me is nothing more than a witch hunt.

@Vouthon: Whether or not the DA's investigation of Lying Pete is a witch hunt, we cannot take Pete's word for it because Pete's word is known to be unreliable.​

In the latter case, Vouthon has a point. That's because the fact Pete routinely lies about stuff is indeed relevant to whether or not Pete's statement is true.

Contemporary logicians recognize three forms of the ad hominem.

The abusive ad hominem: That is, arguing that a position should not be accepted because of some irrelevant negative property of the person who is advocating the position (see above examples).

The circumstantial ad hominem: Arguing that a position should not be accepted because the person advocating the position is doing so only because of a bias on their part brought about by their self-interest or their circumstances. Stephanie argues that more women should be members of Parliament in order to better represent the interests of women. Brandon argues she's only saying that because she's a woman. Brandon's objection is irrelevant to Stephanie's reason why she believes more women should be members of Parliament. In other words, whether or not more women in Parliament would better represent the interests of women logically has nothing to do with whether or not Stephanie holds her view because of some bias on her part.

The tu quoque ad hominem: An argument which attempts to deflect a criticism by pointing out that it applies equally to the accuser. This is the favorite fallacy of small children. "You stole my baseball." "You stole my mitt first." The fact someone stole your baseball is not altered by the fact you stole their mitt first, thus their objection to your claim that they stole your baseball is logically irrelevant.​

All three forms of the ad hominem fallacy have in common that the personal attack is irrelevant to the statement or argument of the person being attacked.
 

Sunstone

De Diablo Del Fora
Premium Member
The SUBJECTIVIST or RELATIVIST fallacy
As God and Darwin intended, there are just two kinds of claims. Objective and subjective.

An objective claim is true or false for everyone. "The earth has a large satellite, sometimes called the moon" is an objective claim. If it's true for one person, it's true for everyone. If it's false for one person, it's false for everyone.

A subjective claim, on the other hand, is not necessarily true or false for everyone. "@Rival loves chocolate, children, and depraved, pseudo-intellectual Bulgarian poets" is a subjective claim. It might be true or false that she loves those things, but whether or not she does has nothing to do with whether or not everyone does.

In essence, the subjectivist fallacy consists in asserting that something which is an objective claim is really a subjective claim. It usually takes the form of a statement to the effect that something is merely an "opinion", "point of view", or "perspective" when in fact it is not merely so.

It can be hard to determine when a subjectivist fallacy has been committed because folks are not always explicit about their reasoning when they do (or don't) commit one. In other words, folks tend to say something vague like, "That's just your point of view", without saying what they mean by it. They could be committing a genuine subjectivist fallacy. But they could also mean by "That's just your point of view" that your view is objectively wrong. If you're curious about whether they are committing a subjectivist fallacy, you should probably ask them for clarification.


Section for those of us who are nerds:

Please note that the definitions of "objective" and "subjective" involved in determining if a line of reasoning commits the subjectivist fallacy have nothing to do with the philosophical claims that "all reality is ultimately subjective", "all knowledge is ultimately subjective", "we are but minds in a vat", etc.etc.etc. Even if any or all of those things were true, there would still be a distinction between claims that are true or false for everyone, and claims that are true or false only for some folks.

In other words, suppose only one human exists in the whole universe, and that human happens to be a brain in a vat created by an evil alien genius named @Woberts. Everything that brain perceives as real is actually an illusion fed to it by the giggling Woberts, whose only other amusement in life is folding paper towels into accordion-like stacks. Even if that were true, it is obvious that Woberts is feeding the brain illusions that include an illusion that some claims are true or false for everyone while some other claims are not. The subjectivist fallacy would still be the fallacy of asserting that a claim that at least appears true for everyone is actually a claim that appears true only for some folks.
 

Sunstone

De Diablo Del Fora
Premium Member
EQUIVOCATION

It is simply a fact that equivocation is a fallacy designed by the devil himself -- more commonly known on RF as @lewisnotmiller -- to sometimes be so subtle that even the best professional logicians fall victim to it.

In essence, the fallacy occurs when a term is used to mean one thing in one portion of an argument and another thing in another portion of an argument.

For example: "Wherever there are laws, there are lawgivers. There are laws in nature. Therefore there must be a cosmic lawgiver."

Here, the equivocation is on the term "laws". The laws that humans (i.e. lawgivers) create are not the same kind of thing as the laws of nature. Human laws are rules known to be created by humans. Natural laws might or might not be created by something, but whether they are or are not is fundamentally unknown -- and probably unknowable. In this case, the fallacy could be avoided if the person making the argument were to first provide a good argument for supposing that natural laws were created by a lawgiver.

Another example: "Sure philosophy helps you argue better, but do we really need to encourage people to argue? There's enough hostility in this world."

The equivocation in this case is on the word "argue". In philosophy, to argue something is to provide reasons for or against a position. But in common speech, to argue often means to dispute or bicker. The fact that philosophy might teach people to provide better reasons for or against something does not necessarily encourage people to dispute or bicker more frequently.

Again, Nigel Warburton gives a more subtle example of possible equivocation in his book, Thinking from A to Z:

1. Equality between all people is impossible because of unavoidable individual differences.
2. Socialism presupposes equality between all people.
3. Therefore, socialism is mistaken.​

Now the argument might or might not involve an equivocation on the term "equality". For instance, it could be the case that "equality" is being defined as "equality of traits or characteristics" (such as intelligence, etc.) in the first use of the word but as "equality of treatment" in the second use of the word. In that case, the argument equivocates on the word "equality". However, that's not the only possible reading.

It could also be the case, for instance, that "equality" is being univocally defined as "equality of traits or characteristics". The argument would then become an exceedingly weak one (because socialism does not presuppose equality of traits or characteristics between all people), but it would not then be a case of equivocation.

Pretty much the only thing to do in a case like this one is ask the position's author to define how he or she is using the term "equality". Unless, of course, you're lewisnotmiller. In which case, you're probably hopping around from one leg to the other while rubbing your hands together and snickering that your invention of the fallacy of equivocation is giving people fits.
 

Sunstone

De Diablo Del Fora
Premium Member
The FALLACY FALLACY

It is widely known among professional logicians everywhere that @YmirGF created the fallacy fallacy in order to defuse justified criticism by @SalixIncendium of his argument. The exchange between the two noble and esteemed RFers -- which took place on this website in the autumn of 2015 -- is now famous:

Ymir: My dear Salix, have you properly considered the fact that Sunstone is most assuredly depraved because he is known to go about in public without pants?

Salix: My fond friend, your conclusion that Sunstone is depraved rests upon an error in your logic. Namely, not everyone who goes about in public without pants is depraved. Some are merely senile, for instance. Thus your notion that Sunstone is depraved rests upon a false dichotomy and cannot possibly be true.

Ymir: Ah! You almost had me there, for I must admit there can be reasons other than depravity why someone would go around in public without pants. However, my good man, I must point out that merely because my reasoning is incorrect is not sufficient grounds by itself to conclude that my conclusion is false. After all, it could be the case that my reasoning is incorrect, but my conclusion is true.

Salix: Zounds! But you are correct, my deer-doting friend. Fallacious reasoning for a conclusion does NOT always mean that the conclusion is false. Moreover, upon thinking about the matter, I can clearly see that Sunstone is indeed depraved. You know, @adrian009 has told me that Sunstone stalks the raccoons in his neighborhood and then photographs them in compromising positions while himself wearing nothing but a tutu and a bandolier holding tubes of K-Y jelly.

Ymir: That's the least of it. Wait till you hear what I've learned of him from @Terese. But first, some wine?

Salix: I don't mind if I do. Now you were saying....
It should be obvious to nearly everyone who thinks about it that it is possible to construct an argument with fallacious reasoning but a true conclusion. Because that is possible, to say that a conclusion must be false because the argument for it contains one or more fallacies of logic is to commit a fallacy.

The fallacy in this case is known as "the fallacy fallacy". Snappy name, eh?

Of course in practice, arguments that contain fallacies tend to have false conclusions. The point, however, is that they do not necessarily have false conclusions.
 

Sunstone

De Diablo Del Fora
Premium Member
MISSING THE POINT

This fallacy has so many names it seems quite possible that it is hiding from the law. Ignoratio elenchi, irrelevant conclusion, red herring, changing the subject, beside the point, clouding the issue, and ignoring the issue are all names either for missing the point, or for closely related fallacies.

In essence the fallacy -- or perhaps category of fallacies -- occurs when someone responds to a statement or argument by changing the subject to another subject that is irrelevant to the original statement or argument.

For example:

@LuisDantas: It is morally wrong to cheat on your spouse. Why on earth did you get up at three in morning to eat all the ice cream in the house?

@sayak83: But what exactly is morality?

Luis: It's a code of conduct shared by a group of people.

Sayak: Who creates the code?​

The original subject of the conversation -- Sayak's heinous and unforgivable act of gobbling up his wife's share of the ice cream -- has derailed into a conversation about the nature of morality. If Sayak now fails to double back at some point in the conversation in order to explain how the nature of morality means it is actually not immoral to gobble up all the ice cream in the house, he will be committing the fallacy of missing the point.

Missing the point is often combined with other fallacies, such as the fallacy of appealing to pity. "Maybe you think he stole your collection of 19th Century wooden legs, but just look at the poor man! Does he look like someone fit to spend five years in prison? Imagine what would happen to his pet gerbil if you pressed charges! Gerbils only live two years. The poor little furry thing would be forced to die alone without his beloved master by his side to comfort him. Do your really want that on your conscience?"

Many logicians define several forms of missing the point in terms of intention. For instance, they say that what makes a red herring fallacy a red herring is that someone intends to divert attention from the original argument by introducing a new argument. But I find the question of intention to be irrelevant to whether or not an argument diverts attention from another argument. It doesn't matter whether it was intended to do so or not -- the effect is the same. Intention is not a matter of logic, it's a matter of psychology.

Last, just about every logician on earth would probably be pissed off at me for lumping all these slightly different fallacies together, and calling all of them the same fallacy -- missing the point. But this thread is meant as a practical guide to better reasoning rather than a taxonomy of logical fallacies. It's true that many of the fallacies named here are indeed a bit different one from the other -- but they all share in one thing: They all divert attention from the original statement or argument in a way that is irrelevant to the original statement or argument.
 

Sunstone

De Diablo Del Fora
Premium Member
POST HOC

The name of this fallacy -- post hoc -- is short for the Latin phrase, Post hoc ergo propter hoc, which means "after this, therefore because of this". As the name suggests, the fallacy consists in arguing that A causes B solely on the basis of the fact that A came before B.

It is obvious that one thing can follow another without the first thing causing the second. Such events happen all the time. Thus, it cannot be reasonably said that A causes B on the sole grounds that B follows A. You need more than that to demonstrate causation.

For example:

Sadly, @Politesse's pet guppy is dying. Politesse calls in three veterinarians, all three of which give the guppy dismal odds of survival. Nevertheless, Politesse desperately prays for it. The guppy not only regains its health, but starts feeling so cocky that it begins suggestively winking at Politesse's cat. Now, regardless of whether or not prayer had a hand in the guppy's recovery, it would be an error in logic to conclude solely on the basis that the guppy recovered after being prayed for that prayer caused the guppy's recovery. You would need more than that to demonstrate causation.​

Another example:

Suppose a new member of the Forum creates a thread asking, "Does God Have Tonsils?" -- not realizing the exact same question has been raised two dozen times on RF in the past year alone.

Next, a moment after super-mod @Vee sees the thread, her computer dies.

Can Vee reasonably ban the new member on the spot for having inflicted massive suffering and misery upon RF's noble and esteemed members? Yes, of course she can. How can such a thread NOT cause untold misery and suffering? But can Vee reasonably ban the new member for killing her computer? Nope, because the mere fact that Vee's computer died immediately after Vee noticed the thread is not sufficient evidence all by itself that the thread killed the computer.​

Logically, post hoc fallacies are often easy to spot. But psychologically, they are often quite hard to resist -- even for very logical people. For example, suppose that one day, @Debater Slayer -- who is pretty darn logical -- goes a whole 24 minutes without even once thinking about women in various stages of undress. Upon realizing he's done such a thing, he is shocked at himself. Justifiably concerned, DS sets off for the hospital on the hunch he might be dying. But on the way there, his foot is run over by a speeding taco truck making an emergency midnight delivery to an university fraternity.

As logical as DS is, he cannot help but wonder whether one of the biggest shocks of his life (his realization that he has not thought about women for a full 24 minutes) had anything to do with the other big shock of his life (having his foot run over). "After all", DS asks himself, "what are the odds of two huge shocks coming so close to together without they being related?" Logically, they are unlikely to be related. But psychologically -- well, that's another matter. Reason tells us one thing, feelings tell us another. Tragically, DS ends up concluding that not thinking of women causes foot injuries, and for the rest of his life, he has a fetish for women's footwear.

Please note: The fact it is a fallacy to reason that A causes B simply because B comes after A does not mean that reasoning A might cause B because B comes after A is a fallacy. The fact that B comes after A can indeed be legitimate evidence that A might cause B. But it should not be taken as sufficient or conclusive evidence. To do so is to commit the post hoc fallacy.
 

Sunstone

De Diablo Del Fora
Premium Member
STRAW MAN


What is a straw man fallacy?


A straw man has this form:

Someone makes an argument, X.

Someone else argues against a different argument, Y, which he or she calls X.

When they refute Y, they claim to have refuted X.​

Here's an example of a straw man argument:

1) Hindus consider the Bhagavad Gita to be a sacred text because it glorifies war.
2) No text that glorifies war can be sacred.
Therefore, the Bhagavad Gita cannot be sacred.​

Now, there are a couple of things to notice about that argument. First, it's a straw man because it misrepresents why Hindus consider the Gita to be a sacred text; and then it refutes that misrepresentation as if it had refuted the real reason(s) Hindus consider the Gita sacred.

Second, it does not logically matter whether or not the person committing the straw man actually intended to commit the straw man. People who commit straw men often consciously intend to commit them. But whether they do or don't intend to commit them, straw men are straw men. Intentions do not change one way or the other the fact a fallacy has been committed.

There are currently at least three kinds of straw men fallacies.

The classical straw man fallacy (the above Gita argument is an example of it) simply misrepresents another argument, goes on to refute the misrepresentation, and then claims to have refuted the original argument.

The weak man fallacy selectively misrepresents another argument. That is, instead of misrepresenting the overall argument, it only misrepresents a key portion of it. The rest it gets correct. This can make it somewhat harder to detect than the classical straw man.

The hollow man fallacy goes well beyond misrepresentation, and fabricates an argument that does not actually exist, along with an opponent that does not actually exist. It then proceeds to refute the fabricated argument by the fabricated opponent. Hollow man arguments often ascribe their fabrications to vaguely described sources such as "some people think", or "someone told me", or "some people inside the women's movement believe", or "some conservatives think that...".

Where did the fallacy get its name?

Actually, the straw man was only identified relatively recently (about 60 years ago -- just about when I was born). People surely committed it before then, but that was the first time the fallacy was actually categorized and defined. Technically, it belongs to a category of fallacies called "informal fallacies", and to a subcategory of those called, "fallacies of relevance".

Despite that it was only relatively recently named, no one really knows how it got its name. There are several stories about how -- but we don't really know which one, if any of them, is true.

Most textbooks I've seen, however, repeat one or another of those stories as if the one they repeat were true. My favorite is that the fallacy was named "the straw man" because the misrepresentation of the original argument is as fake as a straw man.
 
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