9 - Informal Fallacies

9 - Informal Fallacies

Informal Fallacies 1 Formal Vs Informal Fallacies 2 A fallacy is a defect in an argument other than its having false premises. It refers to a defect that is difficult to be detected. An informal fallacy is a defect in the content

of an argument. A formal fallacy is a defect in the structure of an argument. 3 Formal fallacies can be understood as a use of invalid structures that look like valid structures in the first appearance. E.g.:

P Q / Q // P P Q / ~P // ~Q P v Q / P // ~Q Informal Fallacies 4 There are 5 main types of informal fallacies,

comprising a total of 21 cases. A. Fallacies of Irrelevance B. Fallacies of Insufficiency C. Fallacies of Inappropriate Assumption

D. Fallacies of Ambiguity E. Fallacies of Grammatical Analogy Fallacies of Irrelevance 5

THE PREMISES ARE PSYCHOLOGICALLY RELEVANT, BUT NOT LOGICALLY RELEVANT, TO THE CONCLUSION. 1. Appeal to Force 6 Argumentum ad baculum The arguer uses threat instead of evidence to force the listener to accept the conclusion. Example

Student: I deserve an A in the course. You know that my father is a good friend of the College Principal. 2. Appeal to Pity 7 Argumentum ad misericordium The arguer tries to win support by evoking pity from the listener. 3. Appeal to People

8 Argumentum ad populum Direct approach - the arguer excites emotions from the crowd. Indirect approach - the arguer appeals to some individuals by focusing on some aspects of those individuals relationship to the crowd. Direct Approach 9

Most of the political rhetoric uses the direct approach to arouse your favorable impression or resentment. Example Describe CY Leung as a wolf. Label national education as brainwashing education. 3 Types of Indirect Approach

10 A. Bandwagon argument The arguer attempts to persuade the listener by appealing to group pressure. Example Many students choose this course. Therefore, you should also take it. 3 Types of Indirect Approach 11

B. Appeal to vanity Appeal to the pride or conceit of the listener in order to get them to do something. Example Only fools believe what CY Leung says. 3 Types of Indirect Approach 12 C.

Appeal to snobbery Appeal to desire of the listener of being in a particular social class. Example Only the selected few can own a platinum card. 13 14 4. Argument against the Person

15 Argumentum ad hominem The arguer attacks the opponents character instead of his/her argument. 3 types of ad hominem Background attack Circumstance attack You too Background Attach 16

A. Abuse your opponent based on her background. Example CY Leungs words should not be taken because he is a communist. Circumstance attack 17

B. Present your opponent as predisposed to say or act in a certain way because of her circumstance. Example All the policies of CY Leung aim to protect the interests of Mainland because he tries to win the trust of the Central Government. You too 18

C. Argue that doing something is right because your opponent is also doing the same thing. Example Teacher: You should not skip class. Student: I dont think you havent skipped one. 5 Fallacy of Accident

19 Misapply a general rule to a particular case because the particular case is an exceptional case (accident) beyond the scope of the rule. Example Exceeding the speed limit is illegal. Ambulance drivers always exceed the speed limit during

emergency. Thus, their action is illegal. 6. Straw Man 20 During a debate between two sides, one side distorts its opponent's view (usually as a strengthened position) and then attacks the distorted argument. Example

A: The society should not discriminate gays. B: So you are saying the everyone should be homosexual. Its ridiculous! Example 21 When one side argues that Some X are Y, this view can easily be distorted as All X are Y.

Example A: Smoking is bad to health. One of 10 smokers deaths is caused by diseases related to smoking. B: That cannot be true. My grandfather has smoked since he was 16 and he is still very healthy. 7. Fallacy of Missing the Point

22 Ignoratio elenchi This happens when the premises of an argument lead, or seem to lead, to one conclusion but then a completely different conclusion is drawn. Example Many welfare receivers are new immigrants. Therefore, we should

reduce drastically the number of 8. Red Herring 23 During a debate, one side defends his position by stating a seemingly related but in fact irrelevant statement in order to change the subject of discussion.

The truth value of the new statement implies nothing about the truth value of the original position. If the new statement is used to support the original position, the arguer is just missing the point. 24 E.g.: Animal rights activists say that animals are abused in biomedical research labs. But consider this: Pets are abused by their owners every day. Some cases of

abuse are enough to make you sick. 25 A debate may be diverted into a discussion of the personal characteristics of the arguers Consequently, the arguers will also commit the fallacy of attacking against the person. E.g.: A: You should not lie.

B: But why are you so lazy? 26 An arguer may fasten on a trivial point in an opponent's argument, defeating him on that, and then leaving it to be supposed that he has been defeated on the main question. E.g.: A: The Philippine President should apologize to the families of the killed hostages. Ten people were

killed due to the impotence of his government. B: No, you get it wrong. There were eight, not ten, people were killed. 27 An arguer may begin a discussion by stating an extreme position (e.g., All X are Y) and then, when it is attacked, they replace for it a more moderate argument (Some X are Y). E.g.:

A: All the people getting social security assistance are the new immigrants. B: Statistics shows that the majority of those who receive the assistance are single families and seniors. A: But you cannot deny that many of the new immigrants are receiving the assistance. 28

In order to argue that some evil should be tolerated, an arguer may point to some other evil that is worse than the first evil. E.g: A: You should quit smoking. B: You had better ask those drug addicts to stop taking drugs. Fallacies of Insufficiency 29

THE PREMISES ARE NOT STRONG ENOUGH TO JUSTIFY THE CONCLUSION. 9. Appeal to Unqualified Authority 30 Argumentum ad verecundiam The referred-to authority is in fact not an expect. This fallacy is commonly seen in TV shows and advertisements. 31

32 10. Appeal to Ignorance 33 You commit this fallacy if you reason as follows: - Since we cannot prove that P is false, so P is true; or - Since we cannot prove that P is true, so P is

false. Example You cannot prove that CY Leung was lying. So he did not lie. 10. Appeal to Ignorance 34 Some exceptions occur in the courtroom such as the concept of innocent until proven guilty.

But in general, appeal to ignorance is a bad support for your view. 11. Fallacy of Hasty Generalization 35 Small and non-random samples are non- representative (or biased) samples. We commit this fallacy by generalizing nonrepresentative samples into general rules.

Sources of Hasty Generalization 36 1. Small sample size E.g. There is no racial discrimination in the US. Otherwise, Obama cannot be the president. 2. Non-random sampling E.g. 95% of people interviewed in the occupied area support the Occupy Movement. So 95% of HK people support the Occupy Movement.

12. Fallacy of False Cause 37 The link between the conclusion and the premises depends on the assumption of a nonexistent or minor causal connection. Example Tom was seen in the vicinity of the broken window at about the time that it was broken, so he must have done it.

13. Fallacy of Slippery Slope 38 The link between the conclusion and the premises depends on the claim that a certain event will initiate a chain of events leading to some undesirable consequences, and there is no sufficient reason to think that the chain of events will actually take place. When we think too far back or ahead, we fall into the slippery slope. Example

We shouldnt listen to what the animal rights activists say. If they sell us on the idea that pigs have rights, then it will be chickens. Next it will be fishes and other seafood. The starvation of human race will follow close behind. 39 14. Weak Analogy 40 This occurs in an analogical arguments when there

may be differences between the two analogates that can weaken the argument. Example Substances will move from a region of higher concentration to lower concentration. So money will move from the rich to the poor. 41

Fallacies of Inappropriate Presumption 42 THE PREMISES PRESUME WHAT THEY PURPORT TO SHOW 15. Begging the question 43 It presumes the truth of a premise that is

needed to provide adequate support for the conclusion. This fallacy has 3 forms: A) Leave out a crucial premise. E.g.: It is morally impermissible to have abortion because killing innocent human beings is always impermissible. 44

B) Present a premise that more or less has the same meaning as the conclusion. E.g.: Murderers should receive capital punishment, because it is the most just punishment for murder. 45

C) Restate the conclusion as a premise in a long chain of inference. E.g.: Picasso is the greatest artist of the 20th century. Art critics have described him in these terms. These art critics are correct in their assessment because they have a more keenly developed sense of appreciation than laymen. Their sense is trustworthy because, in order to realize Picasso is the greatest artist of the 20th century, that sense is required.

46 16. Fallacy of Complex Question 47 A doubtful proposition is presumed to be acceptable to the respondent when the question is asked. Example 1. How often do you

beat your wife? 2. When was the last time you cheat in the exam? 17. False Dichotomy 48 A dichotomy is a pair of alternatives that are both mutually exclusive and jointly exhaustive. A pair {X, Y} is mutually exclusive if X and Y

cannot both be true. A pair {X, Y} is jointly exhaustive if either X or Y is true. A false dichotomy is committed when the arguer presents a pair of alternatives as if they are a pair of dichotomy. Not Jointly Exhaustive 49 A.

From a disjunctive premise, the arguer can deny one of the alternative and conclude the other. But in fact the alternatives are not jointly exhaustive. Example Either you are clever or you are stupid. Yet you are not clever. So you must be stupid. Not Mutually Exclusive

50 B. One of the alternatives is affirmed and the denial of the other is concluded. But in fact the alternatives are not mutually exclusive. Example Either you are lying or I am lying. Since you are lying, I am not lying.


Killing his wife, the judge sentenced the husband to ten years of imprisonment. 53 B) Ambiguous reference of pronoun to antecedent E.g.:

Jim tells John that he should turn himself in to the police. So John must have committed a crime. 54 C) Missing comma E.g.: The author warns about numerous computational

errors in his accounting book. Therefore, he must have written it very carelessly. 19. Fallacy of equivocation (not included in the textbook) 55 This occurs when a word or a phrase is used in two different meanings. Which word of the following argument has two different meanings?

A good hen is good at reproducing eggs. Therefore, a good person is good at reproducing babies. 56 Which word of the following argument have two different meanings? There is no winning in wars. Take

the example of the WWII. Germany of course was the losing side. But Britain also suffered a great loss in economy, lives, and politics. So it was also the losing side. Fallacies of Grammatical Analogy 57 WRONG TRANSFERENCE OF A CHARACTERISTIC FROM PARTS TO

WHOLE OR VICE VERSA. Distributive and Collective Predication 58 A characteristic is predicated distributively if it is meant to apply to each and every one of the members of the group. A characteristic is predicated collectively if it is

meant to apply to the group taken as a whole. People will die. Will die is predicated distributively to each of the people. Human will extinct. Will extinct is predicated collectively to the whole class of human. 19. Fallacy of Composition 59

This occurs when there is a wrong transference of a characteristic from the parts of something to a whole. Argumentative form Because each member of X has the property P, the whole X also has the property P. Example Everyone will die some day. It follows that human beings will become extinct someday.

Composition vs. Hasty Generalization 60 Dont confuse it with hasty generalization in which the conclusion is not an assertion about a group taken as a whole (collective predication). Rather, it is an assertion about every member of a group (distributive predication). Hasty Generalization proceeds from the specific to the general. Composition proceeds from every member to

the whole class. 20. Fallacy of Division 61 This is the reverse of composition. Now the wrong transference is from whole to parts. Argumentative form Because the whole X has the property P, each member or a member of X also has the property P. Example

Good teachers have almost become extinct. Dr. Wong is a good teacher. So he has almost become extinct. Division vs. Accident 62 Dont confuse with fallacy of accident in which the inference is from a general assertion (distributive predication) to a specific assertion. In the fallacy of division the inference is from an assertion about a

group taken as a whole (collective predication) to an assertion about the members of the group. Accident proceeds from the general to specific. Division proceeds from the whole class to every member.

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