7/27/2019 Fallacies 2011
1/67
FallaciesFlaws in the Structure of an Argument
7/27/2019 Fallacies 2011
2/67
What are fallacies?
Fallacies are defects in an argument.
Fallacies cause an argument to be invalid,unsound, or weak.
Fallacies can be separated into twogeneral groups: formal and informal.
7/27/2019 Fallacies 2011
3/67
Formal Fallacies
Formal fallacies are only found in deductive arguments.
Deductive arguments are supposed to be air-tight.
For a deductive argument to be valid, it must beabsolutely impossible for both its premises to be trueand its conclusion to be false. With a good deductiveargument, that simply cannot happen; the truth of the
premises entails the truth of the conclusion.
7/27/2019 Fallacies 2011
4/67
Formal Fallacies
The classic example of a deductively validargument is: 1. All men are mortal. (premise)
2. Socrates is a man. (premise) 3. Therefore Socrates is mortal. (guaranteed conclusion)
It is simply not possible that both (1) and (2)
are true and (3) is false, so this argument isdeductively valid.
7/27/2019 Fallacies 2011
5/67
Formal Fallacies
Any deductive argument that fails to meet this very highstandard commits a logical error, and so, technically, isfallacious.
This includes many arguments that we would usuallyaccept as good arguments, arguments that make theirconclusions highly probable but not certain.
Arguments that arent deductively valid are said tocommit a formal fallacy.
7/27/2019 Fallacies 2011
6/67
Formal Fallacies
Example of a deductive argument with a formal fallacy:1. All humans are mammals. (premise)2. All cats are mammals. (premise)3. All humans are cats. (conclusion)
Both premises in this argument are true but theconclusion is false. The defect is a formal fallacy and canbe demonstrated by reducing the argument to its bare
structure:1. All A are C
2. All B are C
3. All A are B
7/27/2019 Fallacies 2011
7/67
Formal Fallacies
With deductive arguments, it can behelpful to reduce an argument to itsstructure.All chickens are feathered animals. (premise)
Clucko is a chicken. (premise)
Therefore Clucko is a feathered animal. (guaranteedconclusion)
7/27/2019 Fallacies 2011
8/67
Formal Fallacies
All chickens are feathered animals. (premise)
Quacko is a feathered animal. (premise)
Therefore Quacko is a chicken. (non-guaranteed
conclusion) This argument commits a formal fallacy in that
its form doesnt guarantee the truth of itsconclusion, even if the initial premises are true.
7/27/2019 Fallacies 2011
9/67
The Problem of Conclusiveness in an Argument
Real-world arguments address contestableissues of truth and value that cannot be resolvedwith mathematical certainty.
Disputants can create only more or lesspersuasive arguments, never conclusive ones.
7/27/2019 Fallacies 2011
10/67
The Problem of Conclusiveness in an Argument
Real-worldArguments
Unpersuasive PersuasiveConclusive
Logically soundAir-tight argument
7/27/2019 Fallacies 2011
11/67
Informal Fallacies
They are flaws in the structure of an argument.
They are embedded in many everyday
arguments.
They sometimes make fallacious reasoning seem
deceptively persuasive
7/27/2019 Fallacies 2011
12/67
Why Study Informal Fallacies?
Knowledge of informal fallacies is most useful when werun across arguments that we know are wrong, but wecannot quite say why.
Knowledge of informal fallacies can help you locatespecific weaknesses in others arguments . . . and inyour own!
7/27/2019 Fallacies 2011
13/67
Warning!
Most students who study fallacies begin to find themplentiful in the arguments of those with whom theydisagree.
Realize that fallacies are most likely being used withequal frequency by you, as well as your friends.
Test your integrity by diligently seeking fallacies in yourown arguments.
7/27/2019 Fallacies 2011
14/67
Informal Fallacies: Three Categories
1. Fallacies of Pathos
2. Fallacies of Ethos
3. Fallacies of Logos
7/27/2019 Fallacies 2011
15/67
Fallacies of Pathos
Rest on flaws in the way an argument appeals tothe audiences emotions and values
Argument to the People
Appeal to IgnoranceAppeal to Popularity
Appeal to Pity
Red Herring
7/27/2019 Fallacies 2011
16/67
Argument to the PeopleAppeal to Stirring Symbols
Appeal to the fundamental beliefs, biases, andprejudices of the audience in order to swayopinion through a feeling of solidarity among
those of a group.
7/27/2019 Fallacies 2011
17/67
Argument to the PeopleAppeal to Stirring Symbols
The stirring symbol of the American flag
Allegiance to nationalistic values
Solidarity of American citizens
Ex: Joe Politician delivering a speech while wearing asuit made out material patterned with the American flag.
Ex: Marilyn Manson wiping his butt on an American flag.
7/27/2019 Fallacies 2011
18/67
Appeal to Ignorance
Presenting assumptions, assertions, or evidencethat the audience is incapable of examining or
judging.
Maintaining that because a claim has not beendisproved, it must be true.
7/27/2019 Fallacies 2011
19/67
Appeal to Ignorance
Ex: Researchers have not conclusively shown that thereis no monster at the bottom of Loch Ness; therefore, weshould expect to see the monster at any time.
Ex: There must be intelligent life on other planets. Noone has proven that there isnt.
7/27/2019 Fallacies 2011
20/67
Appeal to Ignorance
Ex: Genetically modified organisms must be dangerousto our health because science has not proved that theyare safe.
Ex: Jones must have used steroids to get those bulging
muscles because he cannot prove that he has not usedsteroids.
7/27/2019 Fallacies 2011
21/67
Appeal to PopularityThe Bandwagon Appeal
The argument rests on the assertion that sinceeverybody else is doing something, you should do it too.
These appeals are fallacious because the popularity ofsomething is irrelevant to its actual merits.
These appeals are common in advertising where theclaim that a product is popular substitutes for evidenceof the products excellence.
7/27/2019 Fallacies 2011
22/67
Appeal to PopularityThe Bandwagon Appeal
Ex: All the popular, cool kids have tattoos; therefore, Ishould get a tattoo.
Ex: Everybody who has a Facebook page has a lot offriends; therefore, I should make a Facebook page.
7/27/2019 Fallacies 2011
23/67
Appeal to PopularityThe Bandwagon Appeal
Ex: Living together before marriage is the rightthing to do because most couples are now doingit.
Ex: You should buy a Toyota Camry because itis the best-selling car in the world.
7/27/2019 Fallacies 2011
24/67
Appeal to Pity
The arguer appeals to the audiencessympathetic feelings in order to support a claimthat should be decided on more relevant or
objective grounds.
7/27/2019 Fallacies 2011
25/67
Appeal to Pity
Ex: Professor Rose, Im sorry I couldnt finish myessay. You dont understand how difficult my life is rightnow. My parents could not afford to send me to college,and I have to work two part-time jobs to pay for my
classes and books.
7/27/2019 Fallacies 2011
26/67
Appeal to Pity
Ex: Honorable Judge, I should not be fined $250 fordriving 85 mph in a 25 mph zone because I wasdistraught from hearing the news of my brothers illnessand was rushing to see him in the hospital.
7/27/2019 Fallacies 2011
27/67
Red Herring
Refers to the practice of throwing an audienceoff track by raising an unrelated or irrelevantpoint.
The name derives from the practice of using a redherring (a very smelly fish) to throw dogs off from ascent that they are supposed to be tracking.
7/27/2019 Fallacies 2011
28/67
Red Herring
Ex: Jacks girlfriend asks, Where were you last night?Jack answers, I sure am glad to see you. You lookextra beautiful today!
Ex: Question to politician, Whats your stand on guncontrol? Politicians reply, Im for family values.
7/27/2019 Fallacies 2011
29/67
Red Herring
Ex: I dont believe we should elect thiscandidate because she would have to put herchildren in daycare.
7/27/2019 Fallacies 2011
30/67
Fallacies of Ethos
Fallacies of Ethos = Rest on a flawedrelationship between the argument and thecharacter of those involved in the argument.
Often these fallacies attack character or usecharacter instead of evidence for proof.
7/27/2019 Fallacies 2011
31/67
Appeal to False Authority
The arguer appeals to the authority of a popular personrather than a knowledgeable one.
Many advertisements are based on this fallacy.
Testimony to support an argument should come from aperson competent in the field.
7/27/2019 Fallacies 2011
32/67
Appeal to False Authority
Kobe Bryant says that Wheaties cereal keeps him on hisgame; therefore, Wheaties cereal is a good cereal.
Real evidence about the quality of Wheaties cereal
would include specific information about its nutritionalcontent rather than testimony from a hired athlete.
7/27/2019 Fallacies 2011
33/67
Appeal to False Authority
My favorite actor, who appeared in a movie about AIDS,has testified that the HIV virus doesnt really cause AIDSand that there has been a cover-up. So, I think thatAIDS must be caused by something other than HIV, and
the drug companies are hiding it so that they can make
money from expensive anti-HIV drugs. The above argument bases its conclusion on the
testimony of an actor, apparently because he appeared
in a movie on the topic. Legitimate testimony on thenature of AIDS would have to come from doctors orscientists.
7/27/2019 Fallacies 2011
34/67
Appeal to False Authority
Tom Cruise says that postpartum depression can be besttreated with vitamins because anti-depressant drugs aredangerous. Therefore, all women who claim they havepostpartum depression should stop taking anti-
depressants and start taking vitamins.
7/27/2019 Fallacies 2011
35/67
Ad HominemAppeal to the person
Arguments that attack the character of thearguer rather than the argument itself Name-calling (referring to a disputant by unsavory
names)Appeal to prejudice (applying ethnic, racial, gender,
or religious slurs to an opponent)
Guilt by association (linking the opposition to
extremely unpopular groups or causes) Poisoning the Well (discrediting an opponent or an
opposing view in advance)
7/27/2019 Fallacies 2011
36/67
Ad HominemAppeal to the person
Name-calling Ex: OJ Simpson claims that he is innocent, but hes a
wife beater.
Ex: Hugh Hefner, founder ofPlayboymagazine, hasargued against the censorship of pornography. ButHefner is an immature, self-indulgent millionaire whonever outgrew the adolescent fantasies of his youth.His argument is worthless.
Ex: All wars are not wrong. The people who say soare cowards.
7/27/2019 Fallacies 2011
37/67
Ad HominemAppeal to the person
Appeal to prejudice Ex: Because he is extremely wealthy, our mayor
cannot properly represent this city.
Ex: I reject what Father Rolly has to say about theethical issues of abortion because he is a Catholicpriest. After all, Father Rolly is required to hold suchviews.
Ex: Of course she is in favor of Affirmative Action.What do you expect from a black woman?
7/27/2019 Fallacies 2011
38/67
Ad HominemAppeal to the person
Guilt by Association Ex: Of course you support medical marijuana. All of
your friends are a bunch of pot-head hippies.
Ex: Professor Smith has argued against the theory ofevolution. But hes a member of the Communist
Bikers Association. I refuse to listen to him!
7/27/2019 Fallacies 2011
39/67
Ad HominemAppeal to the person
Poisoning the Well
Ex: You are told, prior to meeting him, that your friends
boyfriend is a poseur and a mooch. When you meethim, everything you hear him say is tainted.
Ex: Before I leave the floor to the next speaker, I mustremind you that persons who oppose my plan do nothave the best interests of the working people in theirhearts.
7/27/2019 Fallacies 2011
40/67
Straw Man
Greatly oversimplifying an opponents argumentin order to make it easier to refute or ridicule
Diverts attention from the real issue
The name comes from the practice of stuffing dummies andscarecrows with straw. When one attacks an opponent by puttingwords into the opponents mouth, one makes up a dummyposition. But just as beating up a scarecrow doesnt demonstrateany athletic accomplishment, beating up a straw man in an
argument doesnt demonstrate anything.
7/27/2019 Fallacies 2011
41/67
Straw Man
Ex: You many think that levying confiscatory taxes onhomeless peoples cardboard dwellings is the surest wayout of a recession, but I dont.
Ex: While my opponent would like to empty our prisonsof serial killers, I hold to the sacred principles ofcompensatory justice.
7/27/2019 Fallacies 2011
42/67
Fallacies of Logos
Rest on flaws in the relationship amongstatements in an argument
7/27/2019 Fallacies 2011
43/67
Hasty Generalization
Making a broad generalization on the basis oftoo little evidence
Traditionally, faulty generalizations have beenlabeled either hasty or unrepresentative.
7/27/2019 Fallacies 2011
44/67
Hasty Generalization
Ex: Yesterday I met the most remarkable person. He iskind, considerate, sensitive, and thoughtful.
Ex: I talked to five people in my neighborhood, and all
of them said they had guns. The whole city must bearmed.
7/27/2019 Fallacies 2011
45/67
Hasty Generalization
Ex: My cousin is a college student, and he doesnt carethe least bit about politics. Students these days areterribly apathetic.
Ex: Jean writes poetry, and shes very sensitive andfrequently depressed. People who write poetry aresensitive and prone to depression.
7/27/2019 Fallacies 2011
46/67
Post Hoc, Ergo Propter HocAfter This, Therefore Because of This
Occurs when a sequential relationship ismistaken for a causal relationship
Confusing correlation for cause
Ex: Event A occurred before Event B; therefore,Event A must have caused Event B.
7/27/2019 Fallacies 2011
47/67
Post Hoc, Ergo Propter HocAfter This, Therefore Because of This
Ex: Governor X took office in 2008. In 2009,the state suffered a severe recession.Therefore, Governor X should not be re-elected.
Ex: Cramming for a test really helps. Last weekI crammed for a psychology test, and I got an Aon it.
7/27/2019 Fallacies 2011
48/67
Post Hoc, Ergo Propter HocAfter This, Therefore Because of This
Superstition is often based on this fallacy.
Ex: Since I walked under that ladder yesterday, Ive lost
my wallet and received a speeding ticket.
Ex: Everything was going fine until the lunar eclipse lastmonth; thats why the economy is in trouble.
7/27/2019 Fallacies 2011
49/67
Begging the QuestionCircular Reasoning
Supporting a claim with a reason thatsimply restates the claim in differentwords
Ex: Bungee-jumping is dangerous because itsunsafe.
Ex: Women should not be permitted to join mens
clubs because the clubs are for men only.
7/27/2019 Fallacies 2011
50/67
Begging the QuestionCircular Reasoning
Ex: Abortion is murder because it is theintentional taking of the life of a human being.
Because murder is defined as the intentional taking ofthe life of a human being, the argument is circular.
7/27/2019 Fallacies 2011
51/67
False Dilemma Either/Or
Oversimplifying a complex issue so that only two choicesappear possible
No alternative, middle-ground, or compromise positionsare acknowledged.
Often one of the choices is made to seem unacceptable ,so the only remaining option is the other choice. Ex: Its my way or the highway.
7/27/2019 Fallacies 2011
52/67
False Dilemma Either/Or
Ex: Love football or youre not a man.
Ex: A woman can either be a mother or have a
career.
Ex: Either we get tough with drug users, or we
legalize all drugs.
7/27/2019 Fallacies 2011
53/67
False Dilemma Either/Or
Ex: Either we allow embryonic stem cellresearch, or we condemn persons with diabetes,Parkinsons disease, or spinal injuries to a life
without a cure.
7/27/2019 Fallacies 2011
54/67
Slippery Slope
Based on the fear that once we put a foot on aslippery slope heading in the wrong direction,we will have to keep going.
The controlling metaphor is of a slickmountainside without places to hold on ratherthan of a staircase with numerous stoppingplaces.
Often functions as a scare tactic
7/27/2019 Fallacies 2011
55/67
Slippery Slope
Ex: Look, Joe, no one feels worse about yourneed for open-heart surgery than I do. But Istill cannot let you turn this essay in late. If I
were to let you do it, then I would have to leteveryone turn essays in late.
7/27/2019 Fallacies 2011
56/67
Slippery Slope
Ex: We dont dare legalize marijuana. If we do,well have to legalize cocaine, then ecstasy, andthen heroin. Finally, all hard hard drugs will be
available anywhere to anybody.
7/27/2019 Fallacies 2011
57/67
False Analogy
Arguments by analogy use a comparison asthough it were evidence to support a claim.
An argument by analogy is only as strong as thecomparison on which it rests. The false analogyfallacy is committed when the comparison is notstrong enough.
7/27/2019 Fallacies 2011
58/67
False Analogy
Ex: There is no convincing evidence to showthat cigarette smoking is harmful. Too much ofanything is harmful. Too much Jell-O is harmful.
7/27/2019 Fallacies 2011
59/67
False Analogy
Ex: Mountain climber talking to hismother, I dont want to die falling off arock. But you can kill yourself falling in
the bathtub, too.
7/27/2019 Fallacies 2011
60/67
False Analogy
Ex: In his autobiography, Tommy Chong writesthat when DEA (Drug Enforcement
Administration) agents raided his house he saw
himself as Anne Frank talking to Herr Mengele.. . For the first time, I felt like I couldunderstand what the Jews suffered under Hitler,and this was happening in America in 2003.
N S i
7/27/2019 Fallacies 2011
61/67
Non SequiturIt Does Not Follow
Making a claim that does not follow logicallyfrom the premises or is supported by irrelevantpremises.
The arguer seems to make an inexplicablyillogical leap.
There is a disconnect between the reasons andthe claim.
N S it
7/27/2019 Fallacies 2011
62/67
Non SequiturIt Does Not Follow
Ex: Violent video games have some socialvalue because the Army uses them forrecruiting.
There may be an important idea emerging here,
but too many logical steps are missing.
N S it
7/27/2019 Fallacies 2011
63/67
Non SequiturIt Does Not Follow
Ex: Our university has one of the best facultiesin the U.S. because a Nobel Prize winner used toteach here.
How does the fact that a Nobel Prize winner used toteach at our university make its present faculty one ofthe best in the U.S.?
N S it
7/27/2019 Fallacies 2011
64/67
Non SequiturIt Does Not Follow
Ex: Its a beautiful day! We dont need to be inclass.
Ex: The professor in the Hawaiian shirt and flipflops must be an easy grader.
N S it
7/27/2019 Fallacies 2011
65/67
Non SequiturIt Does Not Follow
Ex: The man with the powerful new computermust be highly skilled in the use of computertechnology.
Ex: Emily is on academic probation, but herhours at work have changed, so she will dobetter in her classes now.
N S it
7/27/2019 Fallacies 2011
66/67
Non SequiturIt Does Not Follow
Ex: Donald Trump, the billionaire real-estate developer,in considering a run for president in 2000, told aninterviewer: My entire life, Ive watched politicians bragging about how poor they are, how
they came from nothing, how poor their parents and grandparents were. And I
said to myself, if they can stay so poor for so many generations, maybe this isntthe kind of person we want to be electing to a higher office. How smart canthey be? Theyre morons. Do you want someone who gets to be president andthats literally the highest paying job hes ever had?
As a brief glance at U.S history shows, it does not followthat men of small success in the world of commerce are
unfit to make sound decisions about matters of state.
7/27/2019 Fallacies 2011
67/67
Top Related