Logical Fallacies

[Gost]

Appeal to Novelty

argumentum ad novitatem

(also known as: appeal to the new, ad novitam [sometimes spelled as])

Description: Claiming that something that is new or modern is superior to the status quo, based exclusively on its newness.

Logical Form:

X has been around for years now.

Y is new.

Therefore, Y is better than X.

Example #1:

Two words: New Coke.

Explanation: Those who lived through the Coca-Cola identity crises of the mid eighties know what a mess it was for the company.  In fact, the “New Coke Disaster”, as it is commonly referred to, is literally a textbook example of attempting to fix what isn’t broken.  Coke’s main marketing ploy was appealing to the novelty, and it failed miserably -- even though more people (55%) actually preferred the taste of the New Coke, the old was “better”.

Example #2:

Bill: Hey, did you hear we have a new operating system out now?  It is better than anything else out there because we just released it!

Steve: What’s it called?

Bill: Windows Vista!

Steve: Sounds wonderful!  I can’t wait until all of your users install it on all their computers!

Explanation: For anyone who went through the experience of Vista, this fallacy should hit very close to home.  You were most likely assuming that you were getting a superior product to your old operating system -- you were thinking “upgrade” when, in fact, those who stuck with the status quo (Windows XP) were much better off.

Exception: There are obvious exceptions, like in claiming that your fresh milk is better than your month old milk that is now growing legs in your refrigerator.

Tip: Diets and exercise programs/gadgets are notorious for preying on our desire for novelty.  Don’t be swayed by the “latest research” or latest fads.  Just remember this: burn more calories than you take in, and you will lose weight.

[Gost]

Accident Fallacy

a dicto simpliciter ad dictum secundum quid

(also known as: destroying the exception, dicto secundum quid ad dictum simpliciter, dicto simpliciter, converse accident, reverse accident, fallacy of the general rule, sweeping generalization)

Description: When an attempt is made to apply a general rule to all situations, when clearly there are exceptions to the rule. Simplistic rules or laws rarely take into consideration legitimate exceptions, and to ignore these exceptions is to bypass reason to preserve the illusion of a perfect law. People like simplicity and would often rather keep simplicity at the cost of rationality.

Logical Form:

X is a common and accepted rule.

Therefore, there are no exceptions to X.

Example #1:

I believe one should never deliberately hurt another person, that’s why I can never be a surgeon.

Explanation: Classifying surgery under “hurting” someone, is to ignore the obvious benefits that go with surgery. These kinds of extreme views are rarely built on reason.

Example #2:

The Bible clearly says, “thou shall not bear false witness”, therefore, as a Christian, you better answer the door and tell our drunk neighbor with the shotgun, that his wife, whom he is looking to kill, is hiding in our basement, otherwise you are defying God himself!

Explanation: To assume any law, even divine, applies to every person, in every time, in every situation, even though not explicitly stated, is an assumption not grounded in evidence, and fallacious reasoning.

Exception: Stating the general rule when a good argument can be made that the action in question is a violation of the rule, would not be considered fallacious.

The Bible says, “thou shall not murder”, therefore, as a Christian, you better put that chainsaw down and untie that little kid.

Tip: It is your right to question laws you don’t understand or laws with which you don’t agree.

[Gost]

Ad Fidentia

argumentum ad fidentia

(also known as: against self-confidence)

Description: Attacking the person’s self-confidence in place of the argument or the evidence.

Logical Form:

Person 1 claims that Y is true, but is person 1 really sure about that?

Therefore, Y is false.

Example #1:

Rick: I had a dream last night that I won the lottery! I have $1000 saved up, so I am buying 1000 tickets!

Vic: You know, dreams are not accurate ways to predict the future; they are simply the result of random neurons firing.

Rick: The last time I checked, you are no neurologist or psychologist, so how sure are you that I am not seeing the future?

Vic: It’s possible you can be seeing the future, I guess.

Explanation: Although Vic is trying to reason with his friend, Rick attempts to weaken Vic’s argument by making Vic more unsure of his position. This is a fallacious tactic by Rick, and if Vic falls for it, fallacious reasoning on his part.

Example #2:

Chris: You claim that you don’t believe in the spirit world that is all around us, with spirits coming in and out of us all the time. How can you be sure this is not the case? Are you 100% certain?

Joe: Of course not, how can I be?

Chris: Exactly! One point for me! Biotch!

Joe: What?

Explanation: This is a common fallacy among those who argue for the supernatural or anything else not falsifiable. If Joe was not that reasonable of a thinker, then he might start to question the validity of his position, not based on any new counter evidence presented, but a direct attack on his self-confidence. Fortunately for Joe, he holds no dogmatic beliefs and is perfectly aware of the difference between possibilities and probabilities (see also appeal to possibility).

Exception: When one claims certainty for something where certainty is unknowable, it is your duty to point it out.

Tip: Have confidence that you are probably or even very probably right, but avoid dogmatic certainty at all costs in areas where certainty is unknowable.

[Gost]

Ad Hoc Rescue

ad hoc

(also known as: making stuff up*, MSU fallacy*)

Description: Very often we desperately want to be right and hold on to certain beliefs, despite any evidence presented to the contrary. As a result, we begin to make up excuses as to why our belief could still be true, and is still true, despite the fact that we have no real evidence for what we are making up.

Logical Form:

Claim X is true because of evidence Y.

Evidence Y is demonstrated not to be acceptable evidence.

Therefore, it must be guess Z then, even though there is no evidence for guess Z.

Example #1:

Frieda: I just know that Raymond is just waiting to ask me out.

Edna: He has been seeing Rose for 3 months now.

Frieda: He is just seeing her to make me jealous.

Edna: They’re engaged.

Frieda: Well, that’s just his way of making sure I know about it.

Explanation: Besides being a bit deluded, poor Frieda refuses to accept the evidence that leads to a truth she is not ready to accept. As a result, she creates an ad hoc reason in an attempt to rescue her initial claim.

Example #2:

Mark: The President of the USA is the worst president ever because unemployment has never been so bad before!

Sam: Actually, it was worse in 1982 and far worse in the 1930s. Besides, the President might only be partly responsible for the economy during his term.

Mark: Well... the President kicks animals when nobody is looking.

Explanation: Out of desperation, Mark makes a claim about the President's private treatment of animals after his original claim has been refuted.

Exception: Proposing possible solutions is perfectly acceptable when an argument is suggesting only a possible solution -- especially in a hypothetical situation. For example, “If there is no God, then life is meaningless.” If there is no God who dictates meaning to our lives, perhaps we are truly free to find our own meaning.

Tip: When you suspect people are just making stuff up, rather than providing evidence to support their claim, simply ask them, “What evidence do you have to support that?”

[Gost]

Esco, nitko ti to nece citati... Postavi primjer i link...

Evo ovdje je lijepo na hrvatskom pa nek ljudi virnu, ako ih zanima.

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Uvod

Na internetu postoje milijuni različitih rasprava, no vrlo malo ih ima pravih, kvalitetnih, koji zadovoljavaju kriterije logičke nauke i njenih pravila. Logika je inače, po jednoj od mnogobrojnih definicija znanost o mišljenju. Naravno, poznavanje logike kao nauke nije potrebno da bi se diskutiralo o nečemu, no čak i malo poznavanje je dovoljno da se u raspravi primijete krivi argumenti.

Cjeloviti nauk o formalnoj logici kao takvoj nam na ovom podforumu nije toliko potreban, a i preopširan je za izlaganje (ima tu svega, od tzv. Fuzzy logike, konstruktivne logike, moderne logike etc...). Ovdje je napisano samo ono što će nam dobro doći u bilo kojoj diskusiji na ovom podforumu (a može poslužiti i za druge), pogotovo u onim diskusijama kojima je primarni cilj baš dokazivanje svojeg stajališta. U tom slučaju postoji, da se tako izrazim, posebna vrsta logike, a to je dokazna logika ili logika dijalektike (Booleova logika) koja se bavi isključivo zakonima argumentacije i pogreškama koje se mogu javiti u njima.

Naravno, ovo je samo priručnik, i kada bi se svi strogo držali ovih pravila, diskusija bi ličila na akademsku prepisku. Naravno da se tako što ne traži, niti je potrebno, jer je puno zanimljivije i bolje ako je zabavna atmosfera, a ovo može poslužiti kada želite nekome baš "nabiti na nos" da krivo argumentira i još upotrijebiti latinski izraz .

Što je to argument?

Argument bi bio skup povezanim sudova koji tvore neku tvrdnju. Postoji mnogo vrsta argumenata, a ovdje ćemo prikazati tzv. deduktivne argumente. Deduktivni argumenti su vrlo zgodni, oni su naime najprecizniji, može ih se provjeriti i mogu biti točni (validni) i netočni (invalidni). Deduktivni argument ima tri "faze", premise, inferenciju, i konkluziju. Ovaj dio ćemo popuniti kasnije.

Dokaz

U dokazu se uvijek služimo zaključkom, a često i različitim metodama. Zato se u dokazu mogu pojaviti sve one pogreške koje se pojavljuju u različitim vrstama zaključka i u različitim metodama spoznaje. Međutim, ima nekih pogrešaka koje su karakteristične baš za dokaz. Možemo ih podijeliti u tri glavne grupe: pogreške irelevantnosti, pogreške neosnovanog razloga i pogreške slijeda.

Slijedi lista logičkih pogrešaka


http://www.forum.hr/showthread.php?t=30255

[Gost]

I samo jedna mala napomena... Za konkluziju se veli da je istinita ili neistinita, a za argument koji se katkad zove i zakljuckom (premise + konkluzija) veli se da je valjan, odnosno da nije valjan. To znaci da konkluzija proizlazi iz premisa, odnosno da ne proizlazi...

[Gost]

Ad Hominem (Abusive)

argumentum ad hominem

(also known as: personal abuse, personal attacks, abusive fallacy, damning the source, name calling, needling [form of], refutation by character)

Description: Attacking the person making the argument, rather than the argument itself, when the attack on the person is completely irrelevant to the argument the person is making.

Logical Form:

Person 1 is claiming Y.

Person 1 is a moron.

Therefore, Y is not true.

Example #1:

My opponent suggests that lowering taxes will be a good idea -- this is coming from a woman who eats a pint of Ben and Jerry’s each night!

Explanation: The fact that the woman loves her ice cream, has nothing to do with the lowering of taxes, and therefore, is irrelevant to the argument. Ad hominem attacks are usually made out of desperation when one cannot find a decent counter argument.

Example #2:

Tony wants us to believe that the origin of life was an “accident”. Tony is a godless SOB who has spent more time in jail than in church, so the only information we should consider from him is the best way to make license plates.

Explanation: Tony may be a godless SOB. Perhaps he did spend more time in the joint than in church, but all this is irrelevant to his argument or truth of his claim as to the origin of life.

Exception: When the attack on the person is relevant to the argument, it is not a fallacy. In our first example, if the issue being debated was the elimination of taxes only on Ben and Jerry’s ice cream, then pointing out her eating habits would be strong evidence of a conflict of interest.

Tip: When others verbally attack you, take it as a compliment to the quality of your argument. It is usually a sign of desperation on their part.

Variation: Needling is attempting to make the other person angry, taking attention off of the argument and perhaps even making the other person look foolish.

[Gost]

I samo jedna mala napomena... Za konkluziju se veli da je istinita ili neistinita, a za argument koji se katkad zove i zakljuckom (premise + konkluzija) veli se da je valjan, odnosno da nije valjan. To znaci da konkluzija proizlazi iz premisa, odnosno da ne proizlazi...

pokusavam ovdje neki sazetak svih verbalnih smicalica kojima se ljudi sluze neki vise neki manje. da se mene pita ja bi to uveo kao obavezan predmet u skole osnovne naravno a i srednje umjesto vjeronauka. kad kazemo da je netko elokventan ne uvijek ali cesto je to zabluda jer se osoba sluzi verbalnim smicalicama ne bi li drugu osobu dovela u podredjeni polozaj. ideju mi je dao onaj indjojkin stereotip o muskarcima koji na prvi pogled izgleda vrlo uvjerljivo ili je barem tako samouvjereno napisan kao da je to dogma.

[Gost]

Esco, nitko ti to nece citati... Postavi primjer i link...

Evo ovdje je lijepo na hrvatskom pa nek ljudi virnu, ako ih zanima.

sta me briga za druge citat cu samo ja. na hrvatskom nisam pronasao nista konkretno ili slicno tome. mozda ima ali nisam nasao. necu stavit link jer linka danas ima a sutra ga mozda vise ne bude.

[Gost]

Ad Hominem (Circumstantial)

argumentum ad hominem

(also known as: appeal to motive, conflict of interest, appeal to personal interest, argument from motives, questioning motives, vested interest)

Description: Suggesting that the person who is making the argument is biased, or predisposed to take a particular stance, and therefore, the argument is necessarily invalid.

Logical Form:

Person 1 is claiming Y.

Person 1 has a vested interest in Y being true.

Therefore, Y is false.

Example #1:

Salesman: This car gets better than average gas mileage and is one of the most reliable cars according to Consumer Reports.

Will: I doubt it—you obviously just want to sell me that car.

Explanation: The fact that the salesmen has a vested interest and selling Will the car does not mean that he is lying. He may be, but this is not something you can conclude solely on his interests. It is reasonable to assume that salespeople sell the products and services they do because they believe in them.

Example #2:

Of course your minister says he believes in God. He would be unemployed otherwise.

Explanation: The fact that atheist ministers are about as in demand as hookers who, “just want to be friends”, does not mean that ministers believe in God just because they need a job.

Exception: As the bias or conflict of interest becomes more relevant to the argument, usually signified by a lack of other evidence, the argument is seen as less of a fallacy and more as a legitimate motive. For example, courtesy of Meat Loaf...

Girl: Will you love me forever?

Boy: Let me sleep on it!!!

Girl: Will you love me forever!!!

Boy: I couldn't take it any longer

Lord I was crazed

And when the feeling came upon me

Like a tidal wave

I started swearing to my god and on my mother's grave

That I would love you to the end of time

I swore that I would love you to the end of time!

Tip: When you know you have something to gain from a position you hold (assuming, of course, you are not guilty of this fallacy for holding the position), be upfront about it and bring it up before someone else does.

Supporting this cause is the right thing to do. Yes, as the baseball coach, I will benefit from the new field, but my benefit is negligible compared to the benefit the kids of this town will receive. After all, they are the ones that really matter here.

[Gost]

Pa na ovom linku imas sazetak... Jednostavno opisano. Eventualno, kad uhvatim vremena, mogla bih komentirati svaku pogresku i navesti par boljih primjera... Logika je obavezan predmet u gimnazijama. Rado bih je uvela u sve srednje skole. U osnovne ne bih jer su klinci doista preoptereceni, a i malo je teze shvatljivo za njih.

[Gost]

Ad Hominem (Guilt by Association)

argumentum ad hominem

(also known as: association fallacy, bad company fallacy, company that you keep fallacy, they’re not like us fallacy, transfer fallacy)

Description: When the source is viewed negatively because of its association with another person or group who is already viewed negatively.

Logical Form:

Person 1 states that Y is true.

Person 2 also states that Y is true, and person 2 is a moron.

Therefore, person 1 must be a moron too.

Example #1:

Delores is a big supporter for equal pay for equal work. This is the same policy that all those extreme feminist groups support. Extremists like Delores should not be taken seriously -- at least politically.

Explanation: Making the assumption that Delores is an extreme feminist simply because she supports a policy that virtually every man and woman also support, is fallacious.

Example #2:

Pol Pot, the Cambodian Maoist revolutionary, was against religion, and he was a very bad man. Frankie is against religion; therefore, Frankie also must be a very bad man.

Explanation: The fact that Pol Pot and Frankie share one particular view does not mean they are identical in other ways unrelated, specifically, being a very bad man. Pol Pot was not a bad man because he was against religion, he was a bad man for his genocidal actions.

Exception: If one can demonstrate that the connection between the two characteristics that was inherited by association is causally linked, or the probability of taking on a characteristic would be high, then it would be valid.

Pol Pot, the Cambodian Maoist revolutionary, was genocidal; therefore, he was a very bad man. Frankie is genocidal; therefore, Frankie must also be a very bad man.

[Gost]

Ali poanta je, Esco, da su ovi c/p necitljivi. Ne engleskom su i opsirni. Treba ih prevesti i skratiti. Iznijeti osnove i postaviti link na ova opseznija pojasnjenja. Zato sam i prenijela topic s jednog drugog foruma.

[Gost]

Na primjer ..



Argumentum ad hominem

Najčešći pseudoargument u raspravi, pogotovo u onim "žešćim". Kad netko ne umije pobiti argumentima tvrdnju s kojom se ne slaže, pa je pokušava oboriti pričajući da je onaj koji ju je postavio "poznati lažljivac", "stari pijanac" ili "sin luđaka", i slično, reći ćemo da upotrebljava argumentum ad hominem (argument protiv čovjeka).

Argumentum ad hominem u svojoj "abuzivnoj" (pogrdnoj; uvredljivoj) varijanti sastoji se u tome da se ne raspravlja o spornoj tvrdnji, nego se pokušava diskreditirati čovjek koji je tu tvrdnju postavio.

Postoji međutim i dobroćudnija varijanta ovog argumenta koja ne ide za tim da diskreditira oponenta, nego da ga uvjeri da se on zbog specijalnih okolnosti u kojima se nalazi (zbog svog zanimanja, pripadnosti nekoj političkoj partiji ili društvenoj grupi, svojih ranijih izjava itd.) treba složiti s tezom kojoj oponira.

Ovim argumentom služimo se na primjer, kada u diskusiji sa svećenikom nastojimo pokazati da on, ako ne želi doći u kontradikciju sa Sv. pismom, treba prihvatiti našu tezu ili kada političkog protivnika uvjeravamo da naša teza s kojom polemizira logično proistječe iz nekih teza za koje se on zalaže.

[urbanstyle]

udri ga LI...  

pozz i vama

[Gost]

Pa na ovom linku imas sazetak... Jednostavno opisano. Eventualno, kad uhvatim vremena, mogla bih komentirati svaku pogresku i navesti par boljih primjera... Logika je obavezan predmet u gimnazijama. Rado bih je uvela u sve srednje skole. U osnovne ne bih jer su klinci doista preoptereceni, a i malo je teze shvatljivo za njih.

tnx, nekom ce tvoj link trebati nije lose imati vise izvora znanja. necu sazetke ni resimeauxe. ja sam lik koji je metodican i ide do u atome i detalje atoma. ma ja bih to uveo u skole obavezno pod must. i bilo bi manje nesporazuma, svadja, muljanja itd. svijet je mirniji i ljepsi kad su svi naoruzani a ne samo odabrani neki. mogu se okladit da sve ovo sto ovdje pise nezna 99 % hrvatskih drzavljana. mnogi koriste poneke smicalice spontano poneki su to izucili u detalje isto kao i retoriku i onda to znanje zloupotrebljavaju u komunikaciji a bome i u politici.

[Gost]

Ad Hominem (Tu quoque)

argumentum ad hominem tu quoque

(also known as: “you too” fallacy, hypocrisy, personal inconsistency)

Description: Claiming the argument is flawed by pointing out that the one making the argument is not acting consistently with the claims of the argument.

Logical Form:

Person 1 is claiming that Y is true, but person 1 is acting as if Y is not true.

Therefore, Y must not be true.

Example #1:

Helga: You should not be eating that... it has been scientifically proven that eating fat burgers are no good for your health.

Hugh: You eat fat burgers all the time so that can’t be true.

Explanation: It doesn’t matter (to the truth claim of the argument at least) if Helga follows her own advice or not. While it might appear that the reason she does not follow her own advice is because she doesn’t believe it’s true, it could also be that those fat burgers are just too damn irresistible.

Example #2:

Jimmy Swaggart argued strongly against sexual immorality, yet he has had several affairs with prostitutes; therefore, sexual immorality is acceptable.

Explanation: The fact Jimmy Swaggart likes to play a round of bedroom golf with some local entrepreneurial ladies, is not evidence for sexual immorality in general, only that he is sexually immoral.

Exception: If Jimbo insisted that his actions were in line with sexual morality, then it would be a very germane part of the argument.

Tip: Again, admit when your lack of self-control or will-power has nothing to do with the truth claim of the proposition. The following is what I remember my dad telling me about smoking (he smoked about 4 packs a day since he was 14).

Bo, never be a stupid a--hole like me and start smoking. It is a disgusting habit that I know will eventually kill me. If you never start, you will never miss it.

My dad died at age 69 -- of lung cancer. I never touched a cigarette in my life and never plan to touch one.

[Gost]

Affirmative Conclusion from a Negative Premise

(also known as: illicit negative, drawing a negative conclusion from affirmative premises, fallacy of negative premises)

This is our first fallacy in formal logic out of about a dozen presented in this book. Formal fallacies can be confusing and complex, and are not as common in everyday situations, so please don’t feel lost when reading through the formal fallacies—do your best to understand them as I do my best to make them understandable.

New Terminology:

Syllogism: an argument typically consisting of three parts: a major premise, a minor premise, and a conclusion.

Categorical Term: usually expressed grammatically as a noun or noun phrase, each categorical term designates a class of things.

Categorical Proposition: joins together exactly two categorical terms and asserts that some relationship holds between the classes they designate.

Categorical Syllogism: an argument consisting of exactly three categorical propositions: a major premise, a minor premise, and a conclusion, in which there appear a total of exactly three categorical terms, each of which is used exactly twice.

Description: The conclusion of a standard form categorical syllogism is affirmative, but at least one of the premises is negative. Any valid forms of categorical syllogisms that assert a negative premise must have a negative conclusion.

Logical Form:

Any form of categorical syllogism with an affirmative conclusion and at least one negative premise.

Example #1:

No people under the age of 66 are senior citizens.

No senior citizens are children.

Therefore, all people under the age of 66 are children.

Explanation: In this case, the conclusion is obviously counterfactual although both premises are true. Why? Because this is a categorical syllogism where we have one or more negative premises (i.e., “no people...” and “no senior citizens...”), and we are attempting to draw a positive (affirmative) conclusion (i.e., “all people...”).

Example #2:

No donkeys are fish.

Some asses are donkeys.

Therefore, some asses are fish.

Explanation: This is a categorical syllogism where we have a single negative premise (i.e., “no donkeys”), and we are attempting to draw a positive (affirmative) conclusion (i.e., “some asses”).

Exception: None.

[Gost]

udri ga LI...  

pozz i vama

Heej Oprosti, uopce te nisam vidjela. Zamijetila sam ovu temu koja i je vrlo bitna, ali klasicni c/p samo je cini odbojnom za citanje. No dobro, ako on to zbog sebe arhivira, onda se povlacim, a sve sto sam dosad napisala neka zanemari.

[Gost]

udri ga LI...  

pozz i vama

Heej Oprosti, uopce te nisam vidjela. Zamijetila sam ovu temu koja i je vrlo bitna, ali klasicni c/p samo je cini odbojnom za citanje. No dobro, ako on to zbog sebe arhivira, onda se povlacim, a sve sto sam dosad napisala neka zanemari.

pisi ti sta sad se povlacis. tema je otvorena za sve ali ako cemo o necemu debatirat onda najprije treba nesto i servirat. ja c-p jer sam planetarno poznat po tome i ljudi popizde kad krenem copy paste. ti mozes po svojoj metodi kao sto i ostali mogu kako zele i kako im je jednostavnije. meni je jednostavnije c-p nego prepricavat nesto sto je netko drugi vec obradio i to jako dobro. meni osobno se ne svidjaju hrvatske interpretacije tih smicalica jer su mi nekako sture i povrsne izostavljeni su kljucni detalji da ljudi mogu skuzit na primjerima sta i kako to izgleda. mozemo mi dati primjere nemaproblema.

[Gost]

udri ga LI...  

pozz i vama

ti bi se mogla i pohvalit necime    a i malo vise bit prisutna na forumu.

[Gost]

Affirming a Disjunct

(also known as: the fallacy of the alternative disjunct, false exclusionary disjunct, affirming one disjunct, the fallacy of the alternative syllogism, asserting an alternative, improper disjunctive syllogism, fallacy of the disjunctive syllogism)

New Terminology:

Disjunction: A proposition of the "either/or" form, which is true if one or both of its propositional components is true; otherwise, it is false.

Disjunct: One of the propositional components of a disjunction.

Description: Making the false assumption that when presented with an either/or possibility, that if one of the options is true that the other one must be false. This is when the “or” is not specifically defined as being exclusive.

This fallacy is similar to the unwarranted contrast fallacy.

Logical Form:

P or Q.

P.

Therefore, not Q.



P or Q.

Q.

Therefore, not P.

Example #1:

I can’t stop eating these chocolates. Either I really love chocolate, or I seriously lack will power. I know I really love chocolate; therefore, I cannot lack willpower.

Explanation: Ignoring the possible false dilemma, the fact that one really loves chocolate does not automatically exclude the other possibility of lacking willpower.

Example #2:

I am either going to bed or watching TV. I am exhausted so I will go to bed; therefore, I cannot watch TV.

Explanation: It is logically and physically possible to go to bed and watch TV at the same time, I know that for a fact as I do it just about every night. The “or” does not logically exclude the option that is not chosen.

Exception: If the choices are mutually exclusive, then it can be deduced that the other choice must be false. Again, we are working under the assumption that one of the choices we are given represents the truth.

Today is either Monday or Sunday. It is Monday. Therefore, it is not Sunday.

In formal logic, the above is referred to as a valid disjunctive syllogism.

[Gost]

Affirming the Consequent

(also known as: converse error, fallacy of the consequent, asserting the consequent, affirmation of the consequent)

New Terminology:

Consequent: the propositional component of a conditional proposition whose truth is conditional; or simply put, what comes after the “then” in an “if/then” statement.

Antecedent: the propositional component of a conditional proposition whose truth is the condition for the truth of the consequent; or simply put, what comes after the “if” in an “if/then” statement.

Description: An error in formal logic where if the consequent is said to be true, the antecedent is said to be true, as a result.

Logical Form:

If P then Q.

Q.

Therefore, P.

Example #1:

If taxes are lowered, I will have more money to spend.

I have more money to spend.

Therefore, taxes must have been lowered.

Explanation: I could have had more money to spend simply because I gave up crack-cocaine, prostitute solicitation, and baby-seal-clubbing expeditions.

Example #2:

If it’s brown, flush it down.

I flushed it down.

Therefore, it was brown.

Explanation: No! I did not have to follow the, “if it’s yellow, let it mellow” rule -- in fact if I did follow that rule I would probably still be single. The stated rule is simply, “if it’s brown” (the antecedent), then (implied), “flush it down” (the consequent). From this, we cannot imply that we can ONLY flush it down if it is brown. That is a mistake -- a logical fallacy.

Exception: None.

Tip: If it’s yellow, flush it down too.

[Gost]

Alleged Certainty

(also known as: assuming the conclusion, appeal to common sense [form of])

Description: Asserting a conclusion without evidence or premises, through a statement that makes the conclusion appear certain when, in fact, it is not.

Logical Form:

Everybody knows that X is true.

Therefore, X is true.

Example #1:

People everywhere recognize the need to help the starving children of the world.

Explanation: Actually, people everywhere don’t recognize this. This may seem like common sense to those who make the claim, and to many who hear the claim, but there are many people on this earth who do not share that view, and need to be convinced first.

Example #2:

Everyone knows that, without our culture's religion, we all would be like lost sheep.

Explanation: Everyone does not know that. Sometimes, without stepping outside your own social or cultural sphere, it might seem like what you might accept as universal truths are simply truths within your own social or cultural sphere. Don’t assume universal truths.

Exception: Facts that would seem foolish not to assume, can be assumed -- but one should be prepared to support the assumption, no matter how certain one may be.

We all know that, without water, we cannot survive.

Tip: Replace the word “certain” in your life with “extremely probable”.

Variation: The appeal to common sense is asserting that your conclusion or facts are just “common sense”, yet sense is anything but common. We have a tendency to think that many of our beliefs and opinions are “common sense” when, in fact, they are not. We must argue as to why we believe something is common sense, rather than just asserting that it is.

[Gost]

Alternative Advance

(also known as: lose-lose situation)

Description: When one is presented with just two choices, both of which are essentially the same, just worded differently. This technique is often used in sales. Fallacious reasoning would be committed by the person accepting the options as the only options, which would most likely be on a subconscious level since virtually anyone—if they thought about it—would recognize other options exist.

Example #1:

Max: If you’re not a witch, you have nothing to fear. If you’re not a witch, you are not made of wood; therefore, you will sink and drown after we tie you up and throw you in the well. If you do float, then you are made of wood, you are a witch, and we will hang you.

Glinda: Wait, how is it I have nothing to worry about if I am not a witch?

Explanation: The argument is created so that any woman accused of being a witch will die, which is certainly a lose-lose situation.

Example #2:

Guy working a booth in the mall: Excuse me, but you look like you can use a vacation! Do you have a few minutes to chat about vacation destinations, or would you prefer I just send you some information by e-mail?

Explanation: Of course, other options include just ignoring the guy and keep walking, telling the guy, “no thank you”, and keep walking, or grabbing the guy’s vacation literature, whacking him over the head with it, and then keep walking.

Exception: If you engage your critical thinking and realize other options exist, and still choose one of the given options, you would not be guilty of fallacious reasoning.

Tip: Whenever you are presented with options, carefully consider the possibility of other options not mentioned, and propose them.

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