PDA

View Full Version : The Informal Logical Fallacies


Pyrrho
8th November 2003, 12:56 PM
Primary reference has been "Fundamentals of Logic - Second Edition", by James D. Carney and Richard K. Scheer, (C) 1974 Macmillan Publishing Company, Inc., ISBN 0-02-319430-8

There are more references available on the web.

ad hominem - committed when reasons given for a conclusion are no more than a criticism of a person or their particular circumstances.
tu quoque or "You're Another" - committed when an argument is answered by responding with the same or similar arguments which are irrelevant to the conclusion. Also, when an argument is answered by showing that the opposing party has committed the same error.
ad populum or Appeal to Popularity - the argument is held to be true because it is widely held to be true. "Most people belief in psychic phenomena, so there must be something to it."
ad misericordiam or "Appeal to Pity" or "Appeal to Emotion" - a form of ad populum which attempts to invoke sympathy in order to support a conclusion. "Sure, he might be a fraud, but he's helping people through their grief."
ad baculum or "Appeal to Force" or "Appeal to Consequences" - committed when the argument takes the form of "might makes right" or warns that if the conclusion is not accepted then dire consequences will result. Reported to have been popularized by Al Capone.
ad verecundiam or "Appeal to Authority" - committed when one attempts to support a conclusion by citing some person(s) who already asserts the same conclusion, but who is not qualified to assert that conclusion. Often occurs when the arguer cites themselves as the authority. Note: if the authority cited is a reliable, qualified authority concerning the conclusion, this can be a valid argument. The fallacy lies in citing an authority who is not reliably qualified to assert the conclusion.
ad ignorantiam or "Argument from Ignorance" - committed when the conclusion is asserted as true because there is no proof that it is false, or false when there is no proof that it is true, as in "there is no proof that p is false, therefore p is true" and vice-versa. An exception to this fallacy occurs in the court of law, when a person is presumed innocent until proved guilty. Another exception occurs in the sciences, when a statement may be considered false on the basis of the failure to find evidence for the statement, presupposing that the scientist(s) are sufficiently expert in the area so that if evidence where there, they would find it. "You can't prove it isn't so, so it must be so."
petitio principii or "Begging the Question", "Circular Reasoning" - occurs when an argument is used to suppport itself, as in p is true, therefore p is true, or p is true because q is true, q is true because r is true, and r is true because p is true. The conclusion repeats the reason or premise. "We know the Bible is the word of God because it says so in the Bible."
Complex Question - the arguments presuppose that the conclusion is true. Also known as a "Catch-22" or "double bind" or "forcing the conclusion". Often illustrated by the question, "When did you stop beating your wife?"
Genetic Fallacy - often a variation of ad hominem, The arguer describes what process led someone to a conclusion and infers from that process that the conclusion is false. "He committed several logical fallacies in his argument, so he's wrong when he says that 2 + 2 = 4"
Straw Man - committed when a conclusion is misinterpreted or misrepresented an attempt is made to refute the misinterpreted or misrepresented conclusion. "You say there is no God, so that means you support Satanists. Anything a Satanist says can't be true, so you're wrong!"
post hoc or "False Cause" or "False Analogy" - argument in which one gives an incorrect or unrelated reason for a given conclusion. "You use your mind to move your muscles, don't you? So this proves that mind has control over matter. Uri Geller's power to bend spoons with his mind is therefore real."
Special Pleading - the arguer considers only those reasons which support the conclusion. To avoid this fallacy the arguer must consider reasons both pro and con. "My ideas are being suppressed by the dominant paradigm. We need to change the way science approaches things in order to accomodate my ideas."
Hasty Generalization - committed when the arguer infers from an insufficiently large or quantitatively unrepresentative sample (fallacy of small sample) or when one infers from a peculiarly selected or qualitatively unrepresentative sample (fallacy of biased statistics). "9 out of 10 dentists prefer toothpaste A, based on a survey of 45 dentists."
Equivocation - occurs when words or expressions having multiple meanings are used inconsistently and the correctness of the argument depends on consistent definition. "When I said 'red', I meant 'infrared'. Unless it's blue. It's all subjective anyway."
Fallacy of Division - committed when someone argues that something which is true only of the whole is also true of its parts taken separately.
Fallacy of Composition - committed when someone argues that what is true only of the parts is also true of the whole.
Fallacy of Accent - committed when a statement is accented in a way that changes its meaning, and is used in an argument.
False Dilemma - arguer asserts that there are only two possibilities for a conclusion, when there are actually more.

Iamme
8th November 2003, 03:57 PM
Pyrrho---Go back and read your "Ad verecundiam". No , can you find a site that gives a name to THIS: Someone misspells a word. THEN, a person thinks this is funny and tells the person they misspelled a word, and then misspells the word misspell, by spelling it mispell. Then somebody else jumps into the mix and says that THAT person was misstaken. (spelling error on misstaken) LOL. Is there some "ad (name)" to this?

Pyrrho
8th November 2003, 05:54 PM
Originally posted by Iamme
Pyrrho---Go back and read your "Ad verecundiam". No , can you find a site that gives a name to THIS: Someone misspells a word. THEN, a person thinks this is funny and tells the person they misspelled a word, and then misspells the word misspell, by spelling it mispell. Then somebody else jumps into the mix and says that THAT person was misstaken. (spelling error on misstaken) LOL. Is there some "ad (name)" to this?
I don't know latin for "misspell". :D

UnrepentantSinner
8th November 2003, 10:00 PM
Probo mendiosus. I coined this in Flame War. Erronious judgement. Might have some legs, might not.

Pyrrho, want me to put the OP in the FAQ?

Pyrrho
8th November 2003, 10:00 PM
Originally posted by UnrepentantSinner
Probo mendiosus. I coined this in Flame War. Erronious judgement. Might have some legs, might not.

Pyrrho, want me to put this in the FAQ?
Go ahead.

Yahweh
8th November 2003, 10:06 PM
List of Logical Fallacies (http://www.infidels.org/news/atheism/logic.html).

Right now, if anyone wants to play, Evildave has opened a thread in the Cat Fight Arena. Its similar to thread he opened a while back called "Fallacy Pong", its a fun game.

xouper
8th November 2003, 11:28 PM
What do you call it when someone accuses you of a logical fallacy even though you were stating an opinion but not using it as the basis of an argument? For example:

Pete: Global warming is anthropogenic.

Ralph: You're a moron.

Pete: Argumentum ad hominem.

Ralph: No it's not. I'm not trying to refute your position on the basis of your moronocity. I'm bypassing the argument and simply stating an opinion.

Yahweh
9th November 2003, 12:12 AM
Originally posted by xouper
What do you call it when someone accuses you of a logical fallacy even though you were stating an opinion but not using it as the basis of an argument? For example:
<blockquote>Pete: Global warming is anthropogenic.

Ralph: You're a moron.

Pete: Argumentum ad hominem.

Ralph: No it's not. I'm not trying to refute your position on the basis of your moronocity. I'm bypassing the argument and simply stating an opinion.</blockquote>


Pete's first line is an opinion.

Ralph's response is an opinion presented as an arguement, its also an attack on Pete rather than his opinion.

Pete states that Ralph's response was ill-founded.

Ralph says he wants to justify his opinion by restating that Pete is a moron (circular ad hominem...). He says he's bypassing the arguement by stating an opinion, its irrelevant and proves absolutely nothing. He is trying to justify his logical fallacy with another logical fallacy, that doesnt help much at all.

The fallacy name you are looking for is (probably) called "Argumentum ad logicam (fallacy of fallacy)", it is when one's opinion is treated as the conclusion of an arguement or when one logical fallacy is justified by another logical fallacy. See this example:
"Take the fraction 16/64. Now, cancelling a six on top and a six on the bottom, we get that 16/64 = 1/4."

"Wait a second! You can't just cancel the six!"

"Oh, so you're telling us 16/64 is not equal to 1/4, are you?"

The faulty mathematical reasoning is justified by the ad hominem and strawman maneuver in the last line of the example.

no one in particular
9th November 2003, 12:23 AM
Originally posted by Yahweh

The fallacy name you are looking for is (probably) called "Argumentum ad logicam (fallacy of fallacy)", it is when one's opinion is treated as the conclusion of an arguement or when one logical fallacy is justified by another logical fallacy. The “fallacy fallacy” is when you state that the presented argument is invalid only because it is based on a fallacy. The fun thing is, the logic of an argument has nothing to do with the validity of the argument. I find no fallacies in xouper’s example.

Walter Wayne
9th November 2003, 01:03 AM
Originally posted by xouper
What do you call it when someone accuses you of a logical fallacy even though you were stating an opinion but not using it as the basis of an argument?

I think in that example, the problem with the argument is a false premise. I think the line "Argumentum ad hominem" contains the implicit premise that Ralph is attempting to refute the inital argument. If Pete called it a red herring instead, then that premise would not be an implicit in the conlcusion. IMO.

Walt

Paul C. Anagnostopoulos
9th November 2003, 06:25 PM
In an effort to promote the word I recently coined, I'll add this informal fallacy:

ad Zammitiam: Suggesting that a point could be disproven by systematically disproving every item of anecdotal evidence cited for it.

~~ Paul

7th sextile
10th November 2003, 01:33 AM
A pseudoneoclassical update for the age of the electronic
abacus and the JREF forum:

argumentum capsloccium :an attempt to shout down valid
counter arguments

argumentum sub pontum :pointless debate with a troll,
implying a descent to his/her level

ad homonym : 1)rejecting an argument solely because it
hasn't been spellczeched 2) an unnecessary graeco-
latinism.

ad transvestum :attacking a board administrator's personal
lifestyle choices rather than the substance(if any) of
his arguments

argumentum per latinum :argument based on assumed
but obviously unverifiable future events,technology,
etc.(see teslatron,also unobtanium)

ad hominy : deleting old 7th's postings because of their
corny attempts at humor rather than their mindless
stupidity

de minnimouse :fun if trivial de gustibus argument,
typically about popular entertainment e.g."How Many
Noises Would Robocop Make If He Gave A Papal
Blessing?","If Robin Were Straight,Would He Have Any
Chance with Wonder Woman?",etc.


argumentum contra toto :assertion that someone has an
unfair advantage in debate due to a terminally cute avatar

straw dog :argument that begins with mathematical
precision but ends in multiple homicide

argumentum caro incognito :high quantity argument
posted simultaneously in many,often unrelated threads

pulsare ad equum mortuum :rehashing debates about
gun control,materialism,moderation,etc.

exo argumentum exo :an incendiary annihilation preceded
by and concluding with protestations of personal esteem
and affection

argumentum ex posteriorificium :patently bogus argument
often involving "secret" information,unverifiable
credentials,etc.

fallacy of decomposition :fallacious belief that one has
triumphed in debate when in reality one's opponent
has died of boredom or old age.

post hic :the attempted disavowal of a line of argument
by claiming one was drunk when first posting it

toque qouque :counteraccussation that one's opponent
is also typing under the influence of cannabis and/or
au naturel except for a chef's hat

!Xx+-Rational-+xX!
10th November 2003, 02:24 AM
If any of you decide to start worshipping me then don't use these logical fallacies!

DickK
10th November 2003, 03:53 AM
7th sextile, "straw dog" and "fallacy of decomposition", very, very funny.

xouper
10th November 2003, 04:45 AM
7th sextile: A pseudoneoclassical update for the age of the electronic abacus and the JREF forum:Yet another brilliant piece of wordsmithing. I see renata has already nominated it for the Nov langauge award.

davidsmith73
10th November 2003, 10:23 AM
Its all very well being aware of logical fallacies but one must be careful when accusing people of committing them when in fact they have not.

ad populum or Appeal to Popularity - the argument is held to be true because it is widely held to be true. "Most people belief in psychic phenomena, so there must be something to it."

see this thread (http://www.randi.org/vbulletin/showthread.php?s=&threadid=29907)

Solitaire
10th November 2003, 01:36 PM
Appeal To Evidence A challenge often issued by one side or
another with the expectation that the other side has mind reading
capabilities. An Example of use: "Show me the evidence, please."
Often seen in politics and economics discussion area.

cbish
10th November 2003, 02:19 PM
You forgot the one created here on this board.
Argumentum ad Rectum ;) nuff said!

7th sextile
11th November 2003, 12:25 AM
xouper: gratia in pleno

cbish:you're correct,of course-the delicate Victorian
euphemizer that is old 7th calls that
argumentum ex posterioroficium (or is -ficio ?
shoulda asked Pyrrho to edit my little
Latin and less Greek...)

DickK:Thanks-ah the good oul' days when Sam's
films were controversially violent...