critical thinking slide fallacies su11

8/6/2019 Critical Thinking Slide Fallacies Su11

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Fallaciesy

Fallacies have been studied in both formal andinformal accounts of reasoning.

y Fallacies are for the most part as departures fromcorrect standards of reasoning.

y The traditional way of handling fallacies is to treatthem in a separate chapter.

y This textbook classifies fallacies into two groups:irrelevant premises and unacceptable premises.


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Invalid Deductive Argument forms

Denying the Antecedent

Ifp, then q.

Not p.

Therefore,

not q.

Example:

If Spot barks, a burglar is in

thehouse.Spot does not bark.

Therefore, A burglar is not inthehouse.

Affirming theConsequent

Ifp, then q.q.Therefore, p.

Example:

If Spot barks, a burglar isin the house.A burglar is in the house.Therefore, Spot barks.


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Irrelevant premises

Irrelevant premises have no bearing on the truth of theconclusion.

yAd Hominem (against the person)

yAuthority

y Equivocation

y Consensus

y Ignorancey Red Herring

y Straw Man


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Ad Hominem Argument (Argument Against Person)

Ad Hominem argument is the inverse of argument fromauthority. It says that a statement is false because it is

made by a particular person or group of persons.

Most of what individual asays about a particular subjectmatter Sis false.

asayspabout S._______________________________________________

pis false.


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Fallacious Arguments from Authority

(A)When an authority in one field speaks out his viewson other issues. Famous physicians state theiropinions on moral questions. A football hero

endorses one brand of food.(B) Some persons set themselves up as authorities .

(C) In many branches of knowledge, widespreaddisagreement exists. For example, are birds

descendants of dinosaurs?


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The fallacy of Equivocationy If the conclusion of an argument depends on a shift in

meaning of an ambiguous term, phrase, orgrammatical construction in the context of thatargument, the fallacy of equivocation is committed.

ExampleMad men should not be permitted to make important

decisions concerning the lives of others.

My father is mad.

________________________________________My father should not be permitted to make important

decisions concerning the lives of others.


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Argument from Popularity

A claim is held to be correct, or incorrect, on the ground thatmost people believe, or reject, the assertion.

50 million American cant be wrong.Everyone does it.

Usually , when most people aagree on a claim about asubject matter S, the claim is true.

pis a claim about Sthat most people aagree on.

_____________________________________________pis true.

This is very similar to the form of the argument fromauthority


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The Argument from IgnoranceIt is a fallacy in which a conclusion is supported by an illegitimate appeal

to ignorance, as when it is supposed that something is likely to be truebecause we cannot prove that it is false.

The appeal to ignorance has two forms:

1. C is true, because it has not been shown to be false.

Or

2. C is false, because it has not been shown to be true.

Example

Ann wishes to place a small bird feeder in her yard, in the hope of

attracting robins. Al doesnt like birds and doesnt want a bird feedernext door. He asserts that before Ann is allowed to place a bird feederin her yard, she should have to show that bird feeders are notenvironmental health hazard.


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Red herring fallacyAn argument that uses premises that have no bearing on

the conclusion, but only distract from the real issue.

ExampleWe should vote for the three-strikes-and youre-out crime controlmeasure. Im telling you, crime is a terrible thing when it happens to

you. It causes death, pain, and fear. And I wouldnt want to wish thesethings on anyone.


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Straw man fallacy

The fallacy of distorting, exaggerating, ormisrepresenting an opponents position in order tomake it easier to attack.

ExampleThose who oppose prayer in the classroom want to remove religion from

American life. They want to make it impossible for children to learnanything at all about religion in school, and they want to forbid your

child to privately murmur a silent prayer to herself before she eatslunch or gets on the school bus.


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Fallacious arguments based on irrelevant premises:

Ad Hominem sometimes(against the person)

Authority sometimes

Equivocation always

Popularity most of the times

Ignorance always

Red Herring always

Straw Man always


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Unacceptable premises:

Unacceptable premises are relevant to the conclusionbut are nonetheless dubious in some way.

y

Hasty generalizationy Slippery slope

y False dilemma

y Begging the question


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Hasty generalization:

y This fallacy arises from failing to meet the requirement ofobtaining a large enough sample.

Examples

1. Your friend makes a joke on you. You conclude that he isno longer your friend.

2. You conclude that no one likes artichokes because noneof your friends do.

When we lack the appropriate background information todecide whether a sample is large enough, we should try toacquire the information. If this is not possible, it is betterto suspendjudgment than tojump to a conclusion.


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Analogy and The Slippery Slope

The is another type of arguments that are concerned withmarking distinctions (or failing to make distinctions)among analogous things.

The form of slippery slope arguments is the following:

There is some continuum between X and Y.

I

n terms of that continuum, X and Y differ only by degree.____________________________________________

No meaningful distinction can be drawn between X and Y.


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False Dilemma

y When we ignore a whole range of alternative possibilitiesand focus only on the extremes (for example, best-worst,priceless-worthless, friend-foe), and when we frame anargument in terms of the extremes, we commit the fallacy

of False Dilemma.Example

IfI marry A, then Ill be poor.

IfI marry B, then Ill be bored.

I must marry A or B.

________________________

Therefore, Ill be poor or bored.


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Begging the question:

y This fallacy occurs when the truth of the conclusion isalready assumed in premises that are no more

plausible than the conclusion that they are supposedto support.

ExampleJohn Hinckley should not be excused on grounds of insanity; for no one

should escape punishment for an assassination attempt on the grounds

that he or she is insane.


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Fallacious arguments based on unacceptable premises:

Hasty generalization always

Slippery slope sometimes

False dilemma most of the times

Begging the question always


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Causal Fallacies

1. Confusing cause with temporal order (post hocfallacy): Post hoc is the fallacy of arguing that A isthe cause of B just because B comes later than A.

Example:

Following are the results of a study linking increased rate of suicide tosmoking in a sample of 100,000 females:

Compared with those who had never smoked, women who smoked one to 24cigarettes daily displayed twice the likelihood of committing suicide, andthose smoking 25 or more cigarettes daily exhibited four times the likelihoodof committing suicide.


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y Confusing cause and effect: Sometimes we may realizethat there is a causal relationship between two factors---but we may not know which factor is the cause and

which is the effect.

Example:A football coach who is trying to bring his team out of a slump studies the

statistics of past games. His research on several teams over a number of yearsshows that many more passes and attempted passes are almost always made bythe losing team than by the winning team. From this information, the coachinfers that he can make his team win by restricting the number of passes they

throw.


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1. Ignoring a common cause: A and B might be

regularly connected through some commonunderlying cause C.

Example:

Two students in a large class turn in identical term papers. The teacher accuses

them of copying from one another, even though the students can prove thatthey did not know one another, and had no access to one anothers work. Theteacher maintains that copying could be the only cause of the identical papers.

critical thinking slide fallacies su11

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