Common Fallacies of Logic and Rhetoric

[Mad Pino Rage]

Hopefully, this thread may help people formulate and convey their own thoughts and theories without giving others headaches, relenting to playground bullying, and secretly plotting another member's death.

CREDIT
Written by Pansophist of LivingWithStyle.com
http://forums.livingwithstyle.com/t302838-common-fallacies-logic-and-rhetoric.html

COMMON FALLACIES OF LOGIC AND RHETORIC

(Smith commits all the fallacies in the examples here.)

Ad Hoc

Tap dancing around an argument by making things up as you go along.

Example

Smith: God cures headaches when you pray.
Jones: I prayed, and God did not cure my headache.
Smith: God works in mysterious ways.

(Smith has ignored the counterexample and changed the subject.)​

Ad Hominem

Drawing attention to the arguer rather than the argument.

Example

Jones: If the moon landings weren't a hoax, why aren't there any stars in the pictures of astronauts?
Smith: Are you that clueless? The film emulsions can't compensate for both bright space suits and dim stars.

(Even though Smith is right, Jones' cluelessness is not pertinent to the argument.)​

Ad Ignorantiam

Arguing that something must be true (or false) simply because it hasn't been proven false (or true).

Example

Jones: I believe in God.
Smith: But you haven't proved He exists. Therefore, He doesn't.

(Absence of evidence is not evidence of absence.)​

Ad Logicam

Reaching the right conclusion by accident, or by the wrong means.

Example

Smith: I reduced 16/64 to 1/4 by cancelling out the 6s.

(Right answer, wrong method.)​

Affirmation Of The Consequent

A implies B. B is true, therefore A is true.

Example

Smith: If God designed the universe, we would expect there to be orderly physical laws. There are orderly physical laws, so God must have designed the universe.

(Perhaps orderly physical laws are intrinsic to nature.)​

Amphiboly

Unintelligible exposition due to poor grammar or syntax.

Example

Smith: To make a long story short on government spending, we have too many treasuries and people spend.

(The hell?)​

Anecdote

The use of personal experience as evidence.

Example

Jones: Polls show that 80% of African-Americans oppose gay marriage.
Smith: I know several African-Americans, and none of them oppose gay marriage.

(Smith's experience has no bearing on the fact stated by Jones.)​

Audiatur Et Altera Pars

Leaving certain premises unstated for the purpose of eventual surprise.

Example

Smith: American Indians traditionally lived prosperous lives in relative peace.
Jones: Are you joking? They're the poorest of all demographics and suffered annihilation at the hands of European invaders.
Smith: I meant before Europeans arrived.

(No one can be expected to read Smith's mind.)​

Bifurcation

Also called false dilemma, or false dichotomy, this is the representation of something as having X possibilities when there are in fact more possibilities.

Example

Smith: Either Jesus was a liar or He was the Son of God.

(He could also have been delusional, or misquoted, or any number of other things.)​

Circulus In Demonstrando

Circular argument.

Example

Smith: It's not necessary that God exists, therefore it's possible that He doesn't.

(Smith's conclusion is the same as his premise.)​

Complex Question

The offering of only damning conclusions based on a biased presumption.

Example

Smith: So, Jones, have you stopped abusing your spouse, yes or no?

(Perhaps Jones has never abused his spouse, and therefore has nothing to stop.)​

Composition

Drawing conclusions about the whole based on conclusions about certain parts.

Example

Smith: Mercury and Venus have no moons; therefore, no planet should have any moons.

(Perhaps Mercury and Venus are not representative of the Solar System as a whole.)​

Cum Hoc Ergo Propter Hoc

Since X happened when Y happened, X and Y must be related.

Example

Smith: I was praying for a miracle when my toothache stopped. Therefore, God healed me.

(Maybe the toothache would have stopped anyway.)​

Denial Of The Antecedant

A implies B. A is false, therefore B is false.

Example

Smith: If God would appear to me, I would believe in Him. But He has never appeared to me. Therefore, He must not exist.

(There could be any number of reasons God did not appear to Smith.)​

Dicto Simpliciter

A fallacy of induction, reasoning from the general to the particular.

Example

Jones: I'm a Christian.
Smith: Most Christians don't like atheists. Since you're a Christian and I'm an atheist, you must not like me.

(Jones may be an exception to the rule.)​

Division

The opposite of a composition fallacy — i.e., drawing conclusions about parts based on the whole.

Example

Smith: That mountain looks purple, so it must have purple trees.

(The color of the mountain from a distance is influenced by atmospheric conditions.)​

Equivocation

Using a word or phrase to mean different things in different contexts.

Example

Smith: Since America is the land of the free, we should all get free beer.

("Free" means two different things in those contexts.)​

Fallacies Of Appeal

Appeal to things that are irrelevant to the argument. There are a whole slew of these, from appeal to authority to appeal to pity. These are not always necessarily logical fallacies, but are when they do not bear upon the argument.

Example

Jones: Most climatologists say that global warming is real.
Smith: Yeah, but most Americans say that it isn't.

(Jones' appeal to authority is reasonable, since climatologists are experts on weather. But Smith's appeal is irrelevant.)​

Gambler's Fallacy

The notion that a thing is due to happen because of the law of averages.

Example

Smith: I haven't gotten heads for the last twenty tosses. I'm bound to get heads on this toss!

(The odds of getting heads are still fifty-fifty.)​

Genetic Fallacy

The notion that an argument is corrupt (or valid) because something about its source is corrupt (or valid).

Example

Jones: Thomas Jefferson argued that we all have certain unalienable rights.
Smith: But he owned slaves. We can't trust what he said.

(It is inappropriate to apply a 21st century zeitgeist to an 18th century circumstance.)​

Golden Mean Fallacy

Arguing that since neither extreme is good, something in the middle must be good.

Example

Smith: The left exercises financial tyranny, and the right exercises moral tyranny. Therefore, the correct position is held by the centrist.

(A blending of tyrannies is hardly an improvement.)​

Hasty Induction

Drawing a conclusion based on a sample that is too small or limited.

Example

Smith: These two songs by Elton John suck. Therefore, he must be a lousy composer.

(Perhaps most of Elton John's songs do not suck.)​

Hypostatization

Treating an abstract entity as though it were real.

Example

Jones: Natural selection is one mechanism by which species evolve.
Smith: The fact that species need a guiding hand is evidence of an intelligent creator.

(Natural selection is not a guiding hand. It has no purpose or intent.)​

Ignoratio Elenchi

An unsound conclusion from a valid argument. Basically the opposite of ad logicam.

Example

Smith: Bush spent a lot more money than Kerry, and therefore deserves to be president.

(That might be true if spending money were a qualification for being president.)​

Naturalistic Fallacy

Arguing that a fact leads to a conclusion about a value. This fallacy is insidious because it is cloaked in legitimacy.

Example

Smith: 80% of the prison population is composed of minorities. Therefore, we should not trust anyone who isn't white.

(People may be imprisoned for any number of reasons, from being too poor to afford good lawyers to being railroaded as political threats. Trustworthiness is not an attribute of political clout.)​

No True Scotsman

Disqualifying a sample based on arbitrary prejudice. Be careful to distinguish this from a reasonable prejudice.

Example

Smith: Those war protestors ought to be deported.
Jones: But they are American citizens.
Smith: No true American would protest during a time of war.

(I, for one, do not want Smith deciding who is and who is not a real American.)​

Non Sequitur

A conclusion that does not follow from its argument.

Example

Smith: John is a hard worker, so we should hire his son.

(Just because John works hard does not mean that his son does as well.)​

Petitio Principii

Also known as begging the question. One or more of an argument's premises is found in its conclusion.

Example

Smith: The President put it best in my opinion when he said, "The reason I keep insisting that there was a relationship between Iraq and Saddam and al-Qaida is because there was a relationship between Iraq and al-Qaida."

(But seriously, Bush is a great president. If you don't believe it, just ask him.)​

Poison Well

Attempting to invalidate an argument by pointing out a flaw in something only tangentially related to the argument.

Example

Smith: If you need to be convinced that Christianity is corrupt, just look at Hitler. He was a Christian.

(Even if Hitler was a Christian, he was not a church leader and therefore is not even relevant to the point.)​

Post Hoc Ergo Propter Hoc

The notion that because B followed A, A must have been the cause of B.

Example

Smith: This forum went downhill right after the downloads were taken away.

(It is possible that it would have gone downhill anyway, or for some other reason.)​

Red Herring

The introduction of a distraction for the purpose of derailing an argument.

Example

Jones: Tides are caused by the moon's gravity.
Smith: But what about the moon landings? Do you deny that they were a hoax?

(Smith has effectively changed the subject.)​

Shifted Burden

The burden of proof is always on the person making the assertion.

Example

Smith: Pi must have a repeated pattern somewhere in all that mess of numbers.
Jones: Prove it.
Smith: Prove that it doesn't.

(Smith made the initial assertion. The burden of proof is on him.)​

Slippery Slope

Not always bogus, but when used recklessly this fallacy is similar to the gambler's fallacy.

Example

Jones: Given Bush's track record, it is only a matter of time until we lose more of our liberties.
Smith: At this rate, we'll be worse than North Korea.

(Jones' measured conclusion is reasonable. Smith's wild comment is not.)​

Special Pleading

A violation of the philosophical principle of Relevant Difference, i.e., making the case that something should be an exception to the rule without any just cause.

Example

Jones: We can't hire you because you don't meet our standards.
Smith: But I had an unhappy childhood. Shouldn't you make an exception for me?

(No.)​

Straw Man

Formulating an argument (B) that differs from the argument (A) presented by one's opponent in order to argue against B instead of A.

Example

Jones: Abortion is a matter of a woman's privacy rights.
Smith: So, you're saying that women should be allowed to commit murder?

(No, Jones is saying no such thing.)​

Subjectivism

A fallacy of deduction that posits an unprovable counter-example.

Example

Smith: I know that astral travel works because I've done it.
Jones: Well, I've tried it, and I can't do it.
Smith: You just don't have the necessary psychic power.

(My, aren't you special!)​

Syllogistic Fallacy

Too complex to cover here comprehensively, refer to this resource.

Example

Smith: All insects die. Socrates is dead. Therefore, Socrates was an insect.

(But other things die too.)
​

Tu Quoque

Literally "you too". This is a special case ad hominem holding that one's own bad reasoning or behavior is justified by another's.

Example

Smith: I realize I've been rude, but you were rude too.

(Two wrongs don't make a right.)​

Undistributed Middle

Arguing that some particular commonality implies a broader commonality.

Example

Smith: Since dogs are carbon based life forms and so are cats, it follows that dogs are a form of cat.

(But there are lots of carbon based life forms.)​

 

[Ceroscuro]

...the hell's the point?

 

[Mad Pino Rage]

To try and help the Symposium be a place for serious discussion and debate.

 

[rexxzecutioner]

Yeah there's a big website on this... aaaaand this thread is pointless.

 

[Ceroscuro]

To try and help the Symposium be a place for serious discussion and debate.

Mmm... that'd be nice but I don't see how this helps it.

 

[Mad Pino Rage]

It can give people a general idea of how to express their opinion.

 

[Ceroscuro]

Knowing what they're called doesn't change anything. Most kindergarteners don't know what a preposition is, but I'm damn sure they could use the word 'of' in a sentence. People can express their opinions without a guide.

 

[Mad Pino Rage]

Of course they can. Nobody is enforcing the strict use of this guide, but it allows people to get a better grasp for serious debate and discussion.

 

[Ceroscuro]

I guess I just fail to see how... to me it just puts a name to things people already know. And knowing the name doesn't help debate.

 

[BlackStaticWolf]

It's always nice to know the names of the various logical fallacies so as to be able to dismiss them when they arise.

However, some of the definitions you posted are not entirely accurate. For example, the use of anecdote is only a fallacy when said personal experience is irrelevant to the argument at hand. In the example you posted, it's a fallacy, but if you amend the statement made by Jones as to say all african americans, the use of anecdote is no longer a fallacy. The correctness or incorrectness of anecdote is situational, much like the use of slippery slope arguments.

The example of circular reasoning (circulus in demonstrando) is not actually circular reasoning. Smith's conclusion is that it is possible that God does not exist is based upon the premise that God's existence is not a necessity. The premise and the conclusion are NOT the same, further, it's actually a logically valid inference. Here is a good example of circular reasoning:
"The Bible is infallible because it's the word of God. God exists because the Bible says he does."

Also, the fallacy called undistributed middle is actually a kind of syllogistic fallacy.

 

[ryanwh]

Im guilty of ad hominim in spades
Also I think this thread is interesting, though I suppose argueing the point of a thread like this could be a debate but not a very interesting one.

 

[Roman Candle]

I found it quite interesting :lol:

 

[Mr.Mo]

smith is dumb :P

anyways;
I don't debate anymore, this would have been nice back when I was..

 

[Roman Candle]

Here are a couple of things to consider:

Rhetoric is the art of presenting an argument in a convincing form, using various devices. In fact, it is the art of presenting an argument as having greater logical worth that it naturally would have, particularly if your opponent is inarticulate or takes less advantage of rhetoric. However, after a point, being overly articulate and presenting powerful arguments is equally able to turn people against you, to make them feel threatened and more likely to dispute your claims, not to agree with them. Beautifully ironic.

Also, logic as a means of persuading other people of something is highly flawed. It takes the assumption that people are, on the whole, logical. This is clearly not true. In fact, more often than not, people will start with a conclusion and then present endless logic to justify their claims. This leads into:

Why logic is shit:
Logic is a system of using a set of basic facts, and logically working your way to what the result of these facts are. We, (in theory), present these facts as data. This begs the question as to how so many arguments can procede without the use of a single statistic or piece of evidence, but nevermind that. The limit of logic is the limit of the data that founds it. For instance, the government spends a lot of money making posters to put everywhere saying "Keep your phone hidden" so that no one mugs you and takes it. However, there is a flaw in this: There is no actual evidence that having valuables on display makes you more of a target to randomised muggings. Logic says that if a mugger sees someone with their phone out, they will take it; the information missing is that since so many people carry phones, iPods, etc, nowadays it's easier just to go to a rich area and target someone who seems like an easy hit.

There is so much information to be found on any one debate, that in any area of dispute your logic will be significantly weakened by biast information and misleading statistics. This is, of course, assuming that people only take things as true once a factual basis has been found for it. Take, for example, all the people that believe that women who have abortions are frivolous and have poor decision making skills. Did they decide this based on moral objections? On personal experiance? Or did they actually, in line with logical purity, take this to be true as the result of a survey or statistical analysis? Probably not. In any case, a large amount of information simply cannot be recorded by an impatial scientist. In this case: who decides what is frivolous?

Anecdote v Logic
Few people change their minds in the middle of a pure debate. Partly because of the inherent doubt of the facts reported by the opposition, partly because of the doubt of the motives of the opposition, (if they're arguing with you, they're not very likly to be a very fair mediator), and due to other motives for taking an opinion. Mostly, people seem to believe what they want to believe. It's human nature. Things like Oscam's Razor, (basically saying that the simplest answer is the most likely. Not actually very sound - take, for example, the case of the discovery of more and more 'fundemental' particles), seem to have transmuted into "The answer which requires the least stretch of the mind to endorse is probably right,". A complex answer is not only one which is hard to understand, intellectually, but one which challenges the existing moral standards of a person. In the end, no matter how strong your logical argument, if someone does not have the potential, derived from experiance, to agree with you, they're not going to. Let me give you an example (and yet another example of anecdote :lol. For years I believed that homosexuality was a choice. I myself am bisexual, and it seemed obvious to me that I had just chosen not to deny my latent sexuality. No matter what anyone said to me, I simply believed that they were fooling themselves. It wasn't until I met someone who simply was not turned on, in any way, by men, that I changed my mind. It's not that their logical arguments had had no effect: they helped; but they could not alone move me. A person has to experience their own anecdote, before they can believe anything. As I said before, people fundementally irrational, and given the unreliability of data in terms of giving logic authority, people can rationally argue any irrational case they have. Consider two men who through oration influenced people perhaps more than any others: Plato, and Hitler. One appealed totally to logic, one totally to emotion. While being two opposites, they both used their individual methods to great effect. The human psyke responds to both, and to teach someone something, they have to be given both. A man who is not at all influenced by emotion is called a psychopath.

PS. In case anyone didn't catch this, "Logic is shit" is an exageration.

 

[rexxzecutioner]

This is incredible that the thread remained open and not locked/deleted.

 

[DESIRE]

Well, if it means anything, I see the intent of the thread. When I took Geometry we did a few lessons on logic. Though I didn't see the point and found most of it common sense, some people didn't get it. It's just so that some people can read and recognize flaws in their logic and present a better argument.

 

[Zodiac]

Well written! Very informative and surprisingly fun to read as well! ^_^

 

[AceJP]

i liked it, unfortunalye their is so much , I only read half of it lol