4  Informal Fallacies


Your assignment:
Do not do all of Chapter 4.
Read these sections:   1-12, 16, 18, 24, 27, 28
Do these EXERCISES:
 4-1 all
 4-2 a7, a9,  b2, b3, b8, c6
 4-3 a2, a9, b6, b8



 

4  Informal Fallacies


A.  Fallacies are arguments that tend to persuade, but are actually faulty.
B.  Fallacies are commonly divided into two kinds:

 1.  Formal Fallacies:  Arguments whose forms appear valid to many people which are actually invalid.
 Examples:  Affirming the Consequent
                        Denying the Antecedent
                        A or B,   B  So not A
 2.  Informal Fallacies:  The fault in the argument is not due to a mistake in the reasoning, but rather to a problem with the reasons, or the overall strategy.
C.  Many classes in Informal Logic = (Critical Thinking in the old days) were devoted almost entirely to informal fallacies.
D.  Most modern logic books on critical thinking recognize:
 1.  It is hard to diagnose fallacies exactly by name.  The same argument might arguably commit two or more of the fallacies.
 2.  Developing skills at recognizing informal fallacies does not substantially improve critical thinking skills that can be applied to daily life.

1.  Genetic Fallacy


  Attacking a reason unfairly by citing the cause or origin (or "genetics") of a person's belief.

A.  Usually:  how a person came to believe a statement is irrelevant to whether the statement is true.   So an attack on a reason that cites the cause of the belief in it is usually unfair.

 Cause of the belief in a reason  ±  the reason

B.  Example:
 
 John believes:  Clinton was framed by Ken Starr
 (and he uses this as a reason in one of his arguments)

 It is unfair to complain that his reason was caused by the fact that he is a loyal Democrat.

 He may very well be a loyal Democrat.

 His belief may very well be caused by a prejudice in favor of making any Democrat look good.

 Nevertheless, what he says could be true, and the best way to find out if it is true is not to examine what caused his belief, but to do the appropriate research on the issue at hand.
 

C.  Important point.  Not every case of using information about the origin of a belief to evaluate its truth counts as a mistake, or an instance of the genetic fallacy.

 Example:   Joe believes nothing goes faster than the speed of light.

 The origin of Joe's belief is his study of physics in graduate school.

 Here citing the origin of his belief is relevant to whether the belief is true, because it relates to whether Joe is an authority on the issue.

 When the acceptance of a reason depends on whether the author of the argument is an authority, then citing the origins of the belief can be legitimate.

 The fallacy arises when a person's reason is attacked by citing the origin of the belief in cases where what caused the belief is irrelevant to whether it is true.

 Example:      Joe believes Elvis lives

 Attack:  Joe just believes that because he read the National Enquirer, and the National Inquirer can't be trusted to tell the truth.

This is not the Genetic Fallacy  because the origin of the belief (in this case a source known to be unreliable) is relevant to whether we should accept the belief.



 

2.   Ad Hominem   (Against the Man)


 A.  The worlds 'ad hominem' suggest the nature of the fallacy...

 Instead of attacking a reason, you unfairly attack the person presenting the reason.

 B.  The Genetic Fallacy  could be considered to be a special case of the Ad Hominem Fallacy, because instead of attacking a reason on its own merits, you attack the person (by complaining about the way he or she got the belief).

 C.  Example:

 Aldous Huxley supported Darwin's Theory of Natural Selection.

 Natural selection is false because Huxley believes in it and he is a foul dirty atheist .

 Whether Huxley is or is not an atheist is irrelevant to whether Darwin's theory is true.

 D.  Not every attack on a person is an Ad Hominem fallacy.  It is only a fallacy if the attack on the person is irrelevant to whether we should accept the belief.

 Example:    Darwin's theory is doubtful because the only people who argue for never graduated from high school.
 

 The fact that those who argue for it are not authorities is a reason not to accept their view.    So the attack on the person's credentials as an authority is relevant to the issue.

 Discussing a person's intellectual background can be relevant to whether we accept their view.

 Joe is just plain ignorant.

 However, most other properties of a person are going to be pretty much irrelevant:

 Joe smells.
 Joe is immoral.
 Joe is ugly.
 Joe likes Cher.
 



 

12.  Appeal to Authority


  A.  You attack (or support) a reason by unfairly citing an authority.

 B.  Note: it is NOT a fallacy to appeal to an authority on the topic in question.  This is a GOOD way to evaluate a reason.

 C.  The fallacy comes when the use of the authority is unfair.  How do you tell?   Examine whether the authority in question satisfies the requirements:
  1.  The authority must be an expert on the topic.
  2.  The authority must have no reason to mislead.  3.  The topic should not be so controversial that there are respected authorities on both sides.
 Examples:
  The stock market will rebound because Ann Landers said so.
  There are no black holes because the Pope said so.
  Uri Geller has psychokinetic powers because researchers at Stanford Research Institute said so.
 

D.  Even when appeal to an authority does not meet the above requirements, it may not be a fallacy.

 Example.   My doctor  (who is not an authority on skin lesions)  says:     You should get that growth removed.

   Citing my doctor as an authority in this case is OK, since in the case of skin cancer, it is best to act quickly be cautious (and removing it is relatively easy and safe).

 So the requirements for who counts as an authority depend on the nature of the question, and what the costs of being wrong are.

 Some decisions are ones where we have no time or money to obtain the very best information possible.  That does not mean that decisions based on limited information (poor authorities) can't be good ones.



 

3.  Equivocation


 We have discussed this fallacy already in detail.



 

4.  False Alternatives  (a.k.a.  False Dilemma)

    The fallacy occurs when one of the premises (often a suppressed one) has the form  A or B or ... or C, and this premise is actually false.

 Typically the fallacy occurs in an argument with the form of a Disjunctive Syllogism.

 Example #1     (Slogan from the 60s)
 "You are either part of the solution or part of the problem."
 [You aren't part of the solution.]
 So [You are part of the problem.]

 Example #2:
 You aren't Republican so you must be a Democrat.
 [Everyone is either Republican or Democrat]
 



 
 

5.  Straw Man

 
A.  Imagine somebody making a great fuss showing how brave they are by demolishing a straw man.

B.  The Fallacy of the Straw Man is the opposite of the Principle of Charity.

 Principle of Charity:  Make your opponent's argument as good as it can be.

C. Fallacy of the Straw Man:  Make your opponent's argument look ridiculous so that you can easily demolish it.

D.  Example #1:  (on the issue of abortion)

People for Pro Choice are arguing that we ought to murder little children.

(That is not the position of people who are Pro Choice.)

E.  Example #2:  (on national health care)

People against national health care think that greed for profit can solve all our medical problems.

F.  Politicians are particularly fond of the Straw Man Fallacy.   (It ought to be a black mark against them even to try such a tactic, put the public seems to tolerate it.)
 



 

6.  Hasty Generalization


A.  An inductive argument is one where the premises support a general conclusion with a number of instances.

 50 of the marbles were blue so all are blue.

B.  A hasty generalization is an inductive argument where the principles required for a good argument are not met:
 1) Too few cases.
 2)  The sample is not representative.  HONORARY

C.  Examples:

 4 randomly polled people will vote for Bush so everyone will.

 20 of 20 of my best friends will vote for Bush so everybody will.



 

7.  Post Hoc Propter Hoc

(Fallacy of False Cause)

A.  Arguing that A causes B without sufficient evidence, typically from a mere correlation only.

 Thanksgiving regularly precedes Xmas
 So Thanksgiving causes Xmas.

 Death strongly correlates with drinking poison.
 So Death causes  people to drink poison.

 There is a strong correlation between owing a cigarette lighter and lung cancer.
 So owning a cigarette lighter causes lung cancer.

B.  A strong correlation between A and B may provide some evidence that A causes B, but there are many cautions to worry about.
 
 0) Correlations may occur without causation

 1)  B might cause A.

 2)  Some other factor C might cause B and A.

C.  The best evidence for causation is a theory linking one factor with the other.

Example: cigarettes and cancer.



 

8 - 9   Fallacies of Composition and Division


A.  Wholes have properties that their parts do not or can not have.
 * Committees can have a quorum but people can't.
 * Water can be wet, but water molecules can't.
 *  A nation can have an average family with 2.3 children, but no family can have 2.3 children.
 * A Cadillac is a luxury car, but its radio, tires or windshield can't be luxury cars.

B.  Fallacies of division and composition occur when one unfairly applies properties of groups to individuals (or vice versa).

C.  Examples

 Division

 Indians are disappearing.
 The chief of the Navaho is an Indian.
 So the chief of the Navaho is disappearing.

 Composition

 Molecules are all invisible.
 Tables are composed of molecules.
 So tables are invisible.



 

10.  Begging the Question


A.   You might think that all we need for a convincing argument is soundness:
 1) valid form
 2) true premises

B.  But consider this:

 The Earth is round.  Why do you say that?  Well it just is round.

 The earth is round.
 So the earth is round

C.  This argument is sound, but it is not convincing.  There is a third requirement for a convincing argument:
 3)  The arguments reasons are more obvious than its conclusion.

D.  Example already discussed in class.

The Bible says God exists
God wrote the Bible and wouldn't lie to us.
So God exists.

Premise 2 is not the same as God exists, but for it to be true God would already have to exist.  So the argument is not convincing, since premise is no more obvious than the conclusion.



 

11.  Argument ad Ignorantum

(Argument from Ignorance)


A.  This is arguing from the fact that we do not know A to the conclusion that not A.

B.  Example:

 There is not enough evidence that CFCs cause a loss of ozone.
 So CFCs do not cause the loss of ozone.

C.  Note pointing out that we lack evidence for a convincing case that CFCs are implicated in the ozone hole should cause you to wonder, but it doesn't refute the idea.

It is important to distinguish lacking evidence for A
with having evidence for not A.

D.  Natural selection is a theory and no theory can be proven.
So natural selection is false?
So natural selection is in doubt?
So natural selection is conceivably false.
16.  Complex Question

A.  Asking a question whose answer presupposes something in dispute
(This is a favorite lawyer's trick.)

B.  Examples:

At what speed were you going when you recklessly crashed into the plaintiff's car.

Presupposition: the defendant recklessly crashed into the plaintiff's car.

When did you stop beating your wife.

C.  In court a complex question is improper.  The presupposition of any question must be established in evidence before it can be asked.

D.  "How did you react when you saw the intruder come into your house."
 "Objection"
 "Did you see an intruder come into your house"

E.  A related lawyer trick is to phrase questions in such a way as to affect witness memory.

 How fast was the car going when it (bumped, crashed into) the tree?



 

18.  Inconsistency


A.  Making claims (reasons  usually) that are incompatible.

We need more prisons.
We should spend no more money on prisons.
The prison system is run as efficiently as possible.
So vote for me.



 

24.  Slippery Slope


The Domino Theory:

If the communists get into S. Vietnam, then they will take over the country.
If they take over S. Vietnam then they will get into Laos ad Thailand.
If they get into Laos and Thailand then they will control all of Asia.
If they control all of Asia, they will get the whole world and democracy in America will become extinct.
So if the communists get into S. Vietnam, then they will take over the world and democracy in America will become extinct.

If you fail algebra, then you won't get into a good college.
Without a good college eduction you won't get into the right professional school.
If you don't get the right professional school education then you can't get a good job.
If you don't get a good job your life will be ruined.
So  if you fail algebra, your life will be ruined.



 

27 - 28  Arguments from Emotion (Pity)


A.  Trying to win a case by unfairly appealing to emotions.

B.  Point.  Appeal to emotion is often perfectly reasonable.

C.  Examples:

 Compare these two:
 I deserve (an A, a W) because I have been very sick this term.

 I deserve your sympathy because my parent just died.

 The BMW is the best car because think ho proud you will be to own one.

 Crime is running rampant in Houston streets.  Every minute someone is robbed.  So vote for Joe.

 War is Hell.  It is horrible to see the blood, the gore and hear the anguished screams of horribly wounded women and children.
 So war should be avoided if at all possible.

Bottom line:   Ask whether the emotion is relevant.