IJMC and UDSM PL handout

Fallacies
Fallacies are errors in reasoning. They are divided in some major groups according to the fallacies they represent.

1. Fallacies of Distraction
Each of these fallacies is characterized by the illegitimate use of a logical operator in order to distract the reader from the apparent falsity of a certain proposition. The following fallacies are fallacies of distraction:

1. False Dilemma (misuse of the "or" operator)
A limited number of options (usually two) is given, while in reality there are more options. A false dilemma is an illegitimate use of the "or" operator.

Putting issues or opinions into "black or white" terms is a common instance of this fallacy.
Either you're for me or against me.
America: love it or leave it.
Every person is either wholly good or wholly evil.
Proof: Identify the options given and show (with an example) that there is an additional option.

2. Argument From Ignorance (misuse of the "not"operator)
Arguments of this form assume that since something has not been proven false, it is therefore true. Conversely, such an argument may assume that since something has not been proven true, it is therefore false. (This is a special case of a false dilemma, since it assumes that all propositions must either be known to be true or known to be false.) As Davis writes, "Lack of proof is not proof." (p. 59)

Examples:
Since you cannot prove that ghosts do not exist, they must exist.
Since scientists cannot prove that global warming will occur, it probably won't.
Fred said that he is smarter than Jill, but he didn't prove it, so it must be false.

Proof: Identify the proposition in question. Argue that it may be true even though we don't know whether it is or isn't.

3. Slippery Slope (misuse of the "if-then" operator)

In order to show that a proposition P is unacceptable, a sequence of increasingly unacceptable events is shown to follow from P. A slippery slope is an illegitimate use of the "if-then" operator.

Examples:
If we pass laws against fully-automatic weapons, then it won't be long before we pass laws on all weapons, and then we will begin to restrict other rights, and finally we will end up living in a communist state. Thus, we should not ban fully-automatic weapons.

You should never gamble. Once you start gambling you find it hard to stop. Soon you are spending all your money on gambling, and eventually you will turn to crime to support your earnings.

If I make an exception for you then I have to make an exception for everyone.

Proof: Identify the proposition P being refuted and identify the final event in the series of events. Then show that this final event need not occur as a consequence of P.

4. Complex Question (misuse of the "and" operator).

Definition: Two otherwise unrelated points are conjoined and treated as a single proposition. The reader is expected to accept or reject both together, when in reality one is acceptable while the other is not. A complex question is an illegitimate use of the "and" operator.

Examples:

You should support home education and the God-given right of parents to raise their children according to their own beliefs.

Have you stopped beating your girlfriend?

Have you stopped using illegal sales practices? (This asks two questions: did you use illegal practices, and did you stop?)

Proof: Identify the two propositions illegitimately conjoined and show that believing one does not mean that you have to believe the other.

2. Fallacies that Appeal to Motive in Place of Support

The fallacies in this section have in common the practise of appealing to emotions or other psychological factors. In this way, they do not provide reasons for belief.

The following fallacies are appeals to motive in place of support:

1. Appeal to Force (argumentum ad baculum)
The reader is told that unpleasant consequences will follow if they do not agree with the author.

Examples:
You had better agree that the new company policy is the best bet if you expect to keep your job.

If you wont support me, I will tell your wife where you were last night.

Proof: Identify the threat and the proposition and argue that the threat is unrelated to the truth or falsity of the proposition.


2. Appeal to Pity (argumentum ad misercordiam)
Definition: The reader is told to agree to the proposition because of the pitiful state of the author.

Examples:

How can you say that ball is out? It was so close, and besides, we are down 3 goals to two.

We hope you'll accept our recommendations. We spent the last three months working extra time on it.

Proof: Identify the proposition and the appeal to pity and argue that the pitiful state of the arguer has nothing to do with the truth of the proposition.

3. Appeal to Consequences

Definition: The author points to the disagreeable consequences of holding a particular belief in order to show that this belief is false.

Example:

You can't agree that evolution is true, because if it were, then we would be no better than monkeys and apes.

You must believe in God, for otherwise life would have no meaning. (Perhaps, but it is equally possible that since life has no meaning that God does not exist.)

Proof: Identify the consequences to and argue that what we want to be the case does not affect what is in fact the case.

4. Prejudicial Language sometimes referred as appeal to vanity.

Definition: Loaded or emotive terms are used to attach value or moral goodness to believing the proposition.

Examples:

Right thinking Tanzanians will agree with me that we should have chosen Chokala.

A reasonable person would agree that our income statement is too low.


The proposal is likely to be resisted by the so called opposition in Bunge. (Compare this to: The proposal is likely to be rejected by opposition officials in Bunge.)

Proof: Identify the prejudicial terms used (eg. "Right thinking Tanzanians" or "A reasonable person"). Show that disagreeing with the conclusion does not make a person "wrong thinking" or "unreasonable".

4. Appeal to Popularity (argumentum ad populum)

Definition: A proposition is held to be true because it is widely held to be true or is held to be true by some (usually upper crust) sector of the population. This fallacy is sometimes also called the "Appeal to Emotion" because emotional appeals often sway the population as a whole.

Examples:

If you were beautiful, you could live like us, so buy Super Mkorogo and become beautiful. (Here, the appeal is to the "beautiful people".)

Polls suggest that the CCM will form a new government, so you may as well vote for them.

Everyone knows that Kikwete will become the next president, so why do you persist that an opposition candidate may also win?

3. Fallacies of Changing the Subject

The fallacies involved is that of discussing the person making the argument instead of discussing reasons to believe or disbelieve the conclusion. While on some occasions it is useful to cite authorities, it is almost never appropriate to discuss the person instead of the argument.

The fallacies described in this section are:

1. Attacking the Person (argumentum ad hominem)

Definition:

The person presenting an argument is attacked instead of the argument itself. This takes many forms. For example,the person's character, nationality or religion may be attacked. Alternatively, it may be pointed out that a person stands to gain from a favourable outcome. Or, finally, a person may be attacked by association, or by the company he keeps.

There are three major forms of Attacking the Person:

ad hominem (abusive): instead of attacking an assertion, the argument attacks the person who made the assertion.

ad hominem (circumstantial): instead of attacking an assertion the author points to the relationship between the person making the assertion and the person's circumstances.

ad hominem (tu quoque): this form of attack on the person notes that a person does not practise what he preaches.

Examples:
You may argue that God doesn't exist, but you are just following a fad. (ad hominem abusive)

We should discount what Mbunge Mambo says about taxation because he won't be hurt by the increase. (ad hominem circumstantial)

We should disregard Chama Poa’s argument because they are being funded by the logging industry. (ad hominem circumstantial)

You say I shouldn't drink, but you haven't been sober for more than a year. (ad hominem tu quoque)
Proof:

Identify the attack and show that the character or circumstances of the person has nothing to do with the truth or falsity of the proposition being defended.

2. Appeal to Authority (argumentum ad verecundiam)

Definition:

While sometimes it may be appropriate to cite an authority to support a point, often it is not. In particular, an appeal to authority is inappropriate if:
the person is not qualified to have an expert opinion on the subject,
experts in the field disagree on this issue.
the authority was making a joke, drunk, or otherwise not being serious
A variation of the fallacious appeal to authority is hearsay. An argument from hearsay is an argument which depends on second or third hand sources.

Examples:

Noted psychologist Dr. Frasier Crane recommends that you buy the EZ-Rest Hot Tub.

Economist John Kenneth Galbraith argues that a tight money policy s the best cure for a recession. (Although Galbraith is an expert, not all economists agree on this point.)

We are headed for nuclear war. Last week Ronald Reagan remarked that we begin bombing Russia in five minutes.(Of course, he said it as a joke during a microphone test.)

My friend heard on the news the other day that Neverland will declare war on Tanzania. (This is a case of hearsay; in fact, the reporter said that Neverland would not declare war.)

The Sunday Citizen reported that sales were up 5.9 percent this year. (This is hearsay; we are not in a position to check the Citizen's sources.)

Proof: Show that either (i) the person cited is not an authority in the field, or that (ii) there is general disagreement among the experts in the field on this point.

3. Anonymous Authorities
Definition: The authority in question is not named. This is a type of appeal to authority because when an authority is not named it is impossible to confirm that the authority is an expert. However the fallacy is so common it deserves special mention.

A variation on this fallacy is the appeal to rumour. Because the source of a rumour is typically not known, it is not possible to determine whether to believe the rumour. Very often false and harmful rumours are deliberately started in order to discredit an opponent.

Examples:

A government official said today that the new gun law will be proposed tomorrow.

Experts agree that the best way to prevent nuclear war is to prepare for it.

It is held that there are more than two million needless operations conducted every year.

Rumour has it that the President will declare another holiday in May.

Proof:

Argue that because we don't know the source of the information we have no way to evaluate the reliability of the information.

4. Style Over Substance

Definition: The manner in which an argument (or arguer) is presented is taken to affect the likelihood that the conclusion is true.

Examples:

Salim lost the nomination because of the way he read his speech and the sweat on his forehead.

Mr. Cool knows how to move a crowd. He must be right.

Why don't you take the advice of that nicely dressed young man?

Proof: While it is true that the manner in which an argument is presented will affect whether people believe that its conclusion is true, nonetheless, the truth of the conclusion does not depend on the manner in which the argument is presented. In order to show that this fallacy is being committed, show that the style in this case does not affect the truth or falsity of the conclusion.

4. Inductive Fallacies

Inductive reasoning consists of inferring from the properties of a sample to the properties of a population as a whole.

For example, suppose we have a barrel containing of 1,000 beans. Some of the beans are black and some of the beans are white. Suppose now we take a sample of 100 beans from the barrel and that 50 of them are white and 50 of them are black. Then we could infer inductively that half the beans in the barrel (that is, 500 of them) are black and half are white.

All inductive reasoning depends on the similarity of the sample and the population. The more similar the same is to the population as a whole, the more reliable will be the inductive inference. On the other hand, if the sample is relevantly dissimilar to the population, then the inductive inference will be unreliable.

No inductive inference is perfect. That means that any inductive inference can sometimes fail. Even though the premises are true, the conclusion might be false. Nonetheless, a good inductive inference gives us a reason to believe that the conclusion is probably true.
The following inductive fallacies are described in this section:

1. Hasty Generalization

Definition: The size of the sample is too small to support the conclusion.

Examples:

Fred, the chinga boy, stole my wallet. Thus, all chingas are thieves. (Of course, we shouldn't judge all chingas on the basis of one example.)

I asked six of my friends what they thought of the new presidential hopeful and they agreed that he was a good one. Therefore he is generally popular.

Proof: Identify the size of the sample and the size of the population, then show that the sample size is too small. Note: a formal proof would require a mathematical calculation. This is the subject of probability theory. For now, you must rely on common sense.

2. Unrepresentative Sample
Definition: The sample used in an inductive inference is relevantly different from the population as a whole.

Examples:

To see how Tanzanians will vote in the next election we polled a hundred people in Mlingotini. This shows conclusively that the CCM will sweep the polls. (People in Mlingotini might support JMK and hence more likely to vote for him, than people in the rest of the country.)

The apples on the top of the box look good. The entire box of apples must be good. (Of course, the rotten apples are hidden beneath the surface.)
Proof:

Show how the sample is relevantly different from the population as a whole, then show that because the sample is different, the conclusion is probably different.

3. False Analogy

Definition: In an analogy, two objects (or events), A and B are shown to be similar. Then it is argued that since A has property P, so also B must have property P. An analogy fails when the two objects, A and B, are different in a way which affects whether they both have property P.

Examples:

Employees are like nails. Just as nails must be hit in the head in order to make them work, so must employees.

Government is like business, so just as business must be sensitive primarily to the bottom line, so also must government. (But the objectives of government and business are completely different, so probably they will have to meet different criteria.)

Proof: Identify the two objects or events being compared and the property which both are said to possess. Show that the two objects are different in a way which will affect whether they both have that property.

4. Slothful Induction

Definition: The proper conclusion of an inductive argument is denied despite the evidence to the contrary.

Examples:

Mchizi Max has had twelve accidents in the last six months, yet he insists that it is just a coincidence and not his fault. (Inductively, the evidence is overwhelming that it is his fault.)

Poll after poll shows that the N.D.P will win fewer than ten seats in Parliament. Yet the party leader insists that the party is doing much better than the polls suggest. (The N.D.P. in fact got nine seats.)

Proof: About all you can do in such a case is to point to the strength of the inference.

4. Fallacy of Exclusion

Definition: Important evidence which would undermine an inductive argument is excluded from consideration. The requirement that all relevant information be included is called the "principle of total evidence".

Examples:

Jones is Albertan, and most Albertans vote Tory, so Jones will probably vote Tory. (The information left out is that Jones lives in Edmonton, and that most people in Edmonton vote Liberal or N.D.P.)

The AFC of Arusha will probably win this game because they've won nine out of their last ten. (Eight of the AFC’s wins came over last place teams, and today they are playing the first place team.)

Proof: Give the missing evidence and show that it changes the outcome of the inductive argument. Note that it is not sufficient simply to show that not all of the evidence was included; it must be shown that the missing evidence will change the conclusion.

5. Fallacies Involving Statistical Syllogisms

A statistical generalization is a statement which is usually true, but not always true. Very often these are expressed using the word "most", as in "Most conservatives favour welfare cuts." Sometimes the word "generally" is used, as in "Conservatives generally favour welfare cuts." Or, sometimes, no specific word is used at all, as in: "Conservatives favour welfare cuts."

Fallacies involving statistical generalizations occur because the generalization is not always true. Thus, when an author treats a statistical generalization as though it were always true, the author commits a fallacy.

This section describes the following fallacies involving statistical syllogisms:
Accident

1. Accident

Definition: A general rule is applied when circumstances suggest that an exception to the rule should apply.

Examples:
The law says that you should not travel faster than 50 kph, thus even though your father could not breathe, you should not have traveled faster than 50 kph.

It is good to return things you have borrowed. Therefore, you should return this automatic rifle from the madman you borrowed it from. (Adapted from Plato's Republic, Book I).

Proof: Identify the generalization in question and show that it is not a universal generalization. Then show that the circumstances of this case suggest that the generalization ought not to apply.


2. Converse Accident

Definition:

An exception to a generalization is applied to cases where the generalization should apply.

Examples:
Because we allow terminally ill patients to use heroin, we should allow everyone to use heroin.
Because you allowed Jill, who was hit by a truck, to hand in her assignment late, you should allow the entire class to hand in their assignments late.

Proof: Identify the generalization in question and show how the special case was an exception to the generalization.

6. Causal Fallacies

It is common for arguments to conclude that one thing causes another. But the relation between cause and effect is complex one. It is easy to make a mistake.

In general, we say that a cause C is the cause of an effect E if and only if:
Generally, if C occurs, then E will occur, and
Generally, if C does not occur, then E will not occur ether.
We say "generally" because there are always exceptions. For example, we say that striking the match causes the match to light, because:
Generally, when the match is struck, it lights (except when the match is dunked in water), and
Generally, when the match is not struck, it does not light (except when it is lit with a blowtorch).
Many writers also require that a causal statement be supported with a natural law. For example, the statement that "striking the match causes it to light" is supported by the principle that "friction produces heat, and heat produces fire". The following are causal fallacies:

1. Post Hoc (Because one thing follows another, it is held to cause the other)
Coincidental Correlation (post hoc ergo propter hoc)


Definition:

The name in Latin means "after this therefore because of this". This describes the fallacy. An author commits the fallacy when it is assumed that because one thing follows another that the one thing was caused by the other.

Examples:

Immigration to Alberta from Ontario increased. Soon after, the welfare rolls increased. Therefore, the increased immigration caused the increased welfare rolls.

I took EZ-No-Cold, and two days later, my cold disappeared.

Proof:

Show that the correlation is coincidental by showing that: (i) the effect would have occurred even if the cause did not occur, or (ii) that the effect was caused by something other than the suggested cause.

2. Joint Effect (A purported cause and effect are both the effects of a joint cause)

Definition: One thing is held to cause another when in fact both are the effect of a single underlying cause. This fallacy is often understood as a special case of post hoc ergo prompter hoc.

Examples:
We are experiencing high unemployment which is being caused by a low consumer demand. (In fact, both may be caused by high interest rates.)

You have a fever and this is causing you to break out in spots. (In fact, both symptoms are caused by the measles.)
Proof: Identify the two effects and show that they are caused by the same underlying cause. It is necessary to describe the underlying cause and prove that it causes each symptom.

3. Insignificant (The purported cause is insignificant compared to others)

Genuine but Insignificant Cause


Definition: The object or event identified as the cause of an effect is a genuine cause, but insignificant when compared to the other causes of that event. Note that this fallacy does not apply when all other contributing causes are equally insignificant. Thus, it is not a fallacy to say that you helped cause defeat the Tory government because you voted Reform, for your vote had as much weight as any other vote, and hence is equally a part of the cause.

Examples:
Smoking is causing air pollution in Edmonton. (True, but the effect of smoking is insignificant compared to the effect of auto exhaust.)

By leaving your oven on overnight you are contributing to global warming.

Proof: Identify the much more significant cause.

4. Wrong Direction (The direction between cause and effect is reversed)

Wrong Direction


Definition: The relation between cause and effect is reversed.

Examples:
The increase in AIDS was caused by more sex education. (In fact, the increase in sex education was caused by the spread of AIDS.)
Proof: Give a causal argument showing that the relation between cause and effect has been reversed.

5. Complex Cause (The cause identified is only part of the entire cause)

Definition: The effect is caused by a number of objects or events, of which the cause identified is only a part. A variation of this is the feedback loop where the effect is itself a part of the cause.

Examples:

The accident was caused by the poor location of the bush. (True, but it wouldn't have occurred had the driver not been drunk and the pedestrian not been jaywalking.)

The Challenger explosion was caused by the cold weather. (True, however, it would not have occurred had theO-rings been properly constructed.)

People are in fear because of increased crime. (True, but this has lead people to break the law as a consequence of their fear, which increases crime even more.)

Proof: Show that all of the causes, and not just the one mentioned, are required to produce the effect.

7. Missing the Point

These fallacies have in common a general failure to prove that the conclusion is true.

The following fallacies are cases of missing the point:
1. Begging the Question (The truth of the conclusion is assumed by the premises)
Begging the Question (petitio principii)

Definition: The truth of the conclusion is assumed by the premises. Often, the conclusion is simply restated in the premises in a slightly different form. In more difficult cases, the premise is a consequence of the conclusion.

Examples:

Since I'm not lying, it follows that I'm telling the truth.

We know that God exists, since the holy books say God exists. What the holy books say must be true, since God wrote them and God never lies. (Here, we must agree that God exists in order to believe that God wrote the holy books.)
Proof:

Show that in order to believe that the premises are true we must already agree that the conclusion is true.

2. Irrelevant Conclusion (An argument in defense of one conclusion proves another)
Irrelevant Conclusion (ignoratio elenchi )


Definition: An argument which purports to prove one thing instead proves a different conclusion.

Examples:
You should support the new housing bill. We can't continue to see people living in the streets; we must have cheaper housing. (We may agree that housing s important even though we disagree with the housing bill.)

I say we should support affirmative action. White males have run the country for 500 years. They run most of government and industry today. You can't deny that this sort of discrimination is intolerable. (The author has proven that there is discrimination, but not that affirmative action will end that discrimination.)

Proof: Show that the conclusion proved by the author is not the conclusion that the author set out to prove.

3. Straw Man (The arguer attacks a weak version of an opponent's argument)


Definition: The author attacks an argument which is different from, and usually weaker than, the opposition's best argument.

Examples:

People who opposed the Charlottetown Accord probably just wanted Quebec to separate. But we want Quebec to stay in Canada.

We should have conscription. People don't want to enter the military because they find it an inconvenience. But they should realize that there are more important things than convenience.

Proof: Show that the opposition's argument has been misrepresented by showing that the opposition has a stronger argument. Describe the stronger argument.



8. Fallacies of Ambiguity


The fallacies in this section are all cases where a word or phrase is used unclearly. There are two ways in which this can occur.
The word or phrase may be ambiguous, in which case it has more than one distinct meaning.
The word or phrase may be vague, in which case it has no distinct meaning.
The following are fallacies of ambiguity:
1. Equivocation (The same term is used in two different ways)

Definition: The same word is used with two different meanings.

Examples:
The sign said "fine for parking here", and since it was fine, I parked there.

All child-murderers are inhuman, thus, no child-murderer is human. (From Barker, p. 164; this is called "illicit obversion")

A plane is a carpenter's tool, and the Boeing 737 is a plane, hence the Boeing 737 is a carpenter's tool. (Example borrowed from Davis, p. 58)

Proof: Identify the word which is used twice, then show that a definition which is appropriate for one use of the word would not be appropriate for the second use.

2. Amphiboly (The structure of a sentence allows two different interpretations)

Definition: An amphiboly occurs when the construction of a sentence allows it to have two different meanings.

Examples:

Last night I shot a burglar in my pyjamas.

The Oracle of Delphi told Croseus that if he pursued the war he would destroy a mighty kingdom. (What theOracle did not mention was that the kingdom he destroyed would be his own. Adapted from Heroditus, TheHistories.)

Proof: Identify the ambiguous phrase and show the two possible interpretations.

3. Accent

Definition: Emphasis is used to suggest a meaning different from the actual content of the proposition.


Examples:
It would be illegal to give away
Free Beer!

The first mate, seeking revenge on the captain, wrote in his journal, "The Captain was sober today." (He suggests, by his emphasis, that the Captain is usually drunk. From Copi, p. 117)

9. Category Errors


These fallacies occur because the author mistakenly assumes that the whole is nothing more than the sum of its parts. However, things joined together may have different properties as a whole than any of them do separately. The following fallacies are category errors:
1. Composition (Because the parts have a property, the whole is said to have that property)

Definition: Because the parts of a whole have a certain property, it is argued that the whole has that property. That whole maybe either an object composed of different parts, or it may be a collection or set of individual members.

Examples:
The brick wall is six feet tall. Thus, the bricks in the wall are six feet tall.

Germany is a militant country. Thus, each German is militant.

Conventional bombs did more damage in W.W. II than nuclear bombs. Thus, a conventional bomb is more dangerous than a nuclear bomb. (From Copi, p. 118)
Proof: Show that the properties in question are the properties of the whole, and not of each part or member or the whole. If necessary, describe the parts to show that they could not have the properties of the
2. Division (Because the whole has a property, the parts are said to have that property)

Definition: Because the whole has a certain property, it is argued that the parts have that property. The whole in question maybe either a whole object or a collection or set of individual members.

Examples:
Each brick is three inches high, thus, the brick wall is three inches high.
Because the brain is capable of consciousness, each neural cell in the brain must be capable of consciousness.
Proof:

Show that the properties in question are the properties of the parts, and not of the whole. If necessary, describe the parts to show that they could not have the properties of the whole.

10. Non-Sequitur


The term non sequitur literally means "it does not follow". In this section we describe fallacies which occur as a consequence of invalid arguments. The following fallacies are non sequiturs:
1. Affirming the Consequent: any argument of the form: If P then Q, Q, therefore P.

2. Denying the Antecedent: any argument of the form: If P then Q, Not P, thus Not Q.

3. Inconsistency

Definition: The author asserts more than one proposition such that the propositions cannot all be true. In such a case, the propositions may be contradictories or they may be contraries.

Examples:
Montreal is about 200 km from Ottawa, while Toronto is 400 km from Ottawa. Toronto is closer to Ottawa than Montreal.
John is taller than Jake, and Jake is taller than Fred, while Fred is taller than John.
Proof:

Assume that one of the statements is true, and then use it as a premise to show that one of the other statements is false.

11. Syllogistic Errors
Fallacy of Four Terms: a syllogism has four terms

Undistributed Middle: two separate categories are said to be connected because they share a common property

Illicit Major: the predicate of the conclusion talks about all of something, but the premises only mention some cases of the term in the predicate

Illicit Minor: the subject of the conclusion talks about all of something, but the premises only mention some cases of the term in the subject

Fallacy of Exclusive Premises: a syllogism has two negative premises

Fallacy of Drawing an Affirmative Conclusion From a Negative Premise: as the name implies

Existential Fallacy: a particular conclusion is drawn from universal premises

12. Fallacies of Explanation
Subverted Support (The phenomenon being explained doesn't exist)

Non-support (Evidence for the phenomenon being explained is biased)

Untestability (The theory which explains cannot be tested)

Limited Scope (The theory which explains can only explain one thing)

Limited Depth (The theory which explains does not appeal to underlying causes)

13. Fallacies of Definition

Too Broad (The definition includes items which should not be included)

Too Narrow (The definition does not include all the items which should be included)

Failure to Elucidate (The definition is more difficult to understand than the word or concept being defined)

Circular Definition (The definition includes the term being defined as a part of the definition)

Conflicting Conditions (The definition is self-contradictory)