Logical Principles: Informal Fallacies

Fallacies of Grammatical Analogy

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Include composition and division. Arguments that commit this fallacies are grammatically analogous to other arguments that are good in every respect. They may appear good yet bad.

21. Composition
Committed when the conclusion of an argument depends on the erroneous tranference of an attribute from parts of something onto the whole. This fallacy occurs when it is argued that because the parts have a certain attribute, it follows that the whole has that attribute too and the situation is such that attribute in question cannot be legitimately transferred from parts to whole.

Example:
Maria like anchovies. She also likes chocolate ice cream. Therefore, it is certain that she would like a chocolate sundae topped with anchovies.

Sodium and Chlorine, the atomic component of salt, are deadly poisons. Therefore, salt is a deadly poison.

22. Division
It is the exact reverse as composition. Division goes from whole to parts.The fallacy is committed when the conclusion of an argument depends on the erroneous tranference of an attribute from whole (or class) onto its parts (or members).

Example:
Salt is nonpoisonous compund. Therefore, its component element, sodium and chlorine, are nonpoisonous.

The Royal Society is over 300 years old. Prefessor Thompson is a member of the Royal Society. Therefore, Professor Thompson is over 300 years old.

Fallacies of Ambiguity

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Include equivocation and amphiboly. This fallacies arise from the occurrence of some form of ambiguity in either the premises or the conclusion (or both).

19. Equivocation
Occurs when the conclusion of an argument depends on the fact that a word or phrase is used, either explicitly or implicitly, in 2 different sense in the argument.

Example:
Some triangles are obtuse. Whatever is obtuse is ignorant. Therefore some triangles are ignorant.

A mouse is an animal. Therefore a large mouse is a large animal.

20. Amphiboly
Occurs when the arguer misinterprets an ambigious statement and then draws a conclsion base on this faulty interpretation. The original statement is usually asserted by someone other than the arguer, and the ambiguity usually arise from a mistake in grammar or punctuation. Ambiguity in sentence structure.

Example:
The tour guide said that standing in Greenwich Village, the Empire Sate Building could easily be seen. It follows that the Empire State Building is in Greenwich Village.

John told Henry that he has made a mistake. It follows that John has at least the courage to admit his own mistakes.

Fallacies of Presumption

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This fallacy include begging the question, complex question, false dichotomy, and suppressed evidence. This fallacies arise because the premises presume what they purport to prove.

15. Begging the Question (Petitio Principii)
Committed whenever the arguer creates the illusion that inadequate premises provide adequate support for the conclusion by leaving out a possible false (shaky) premise, by restating possibly false premiseas the conclusiuon or by reasoning in a circle. There are 3 types this fallacy can occur.

a. leaving out a possible false key premise
It is the most common form for this fallacy. It leaves out a possible false key premise out of the argument while creating the illusion that nothing more is needed to establish the conclsion.
Example: Murder is morally wrong. This being the case, it follows that abortion is morally worong.
b. Paraphrasing
The conclsion of the argument merelt restates a possible false premise in slightly different language.
Example: Anyone who preaches revolution has a vision of the future for the simple reason that if a person has no vision of the future he could could not possible preach revolution.
c. Circular Reasoning
In a chain of inferences the first premise is possibly false.
Example: Ford Motor Company clearly produces the fnist cars in the US. We know they produce the finest cars because they have the best design engineers. This is true because they can afford to pay them more that other manufacturers. Obviously they can afford to pay them more because they produce the finest cars in the US.
16. Complex Question
It is committed when 2 or more questions are asked in the guise of a single question and a single answer is then given to both of them.

Example:
Have you stopped cheating on exams?
Where did you hide the marijuana you were smoking?

17. False Dichotomy (dilemma)
When a disjunctive ("either...or...") premise presents 2 unlikely alternatives as if they were the only ones available, and the arguer then eliminates the undesirable alternative, leaving the desirable one as the conclusion.

Example: Either you let me attenf the Dixie Chicks concert ot I'll me miserable for the rest of my life. I know you dont want me to be miserable for the rest of my life, so it follows that you'll let me attend the concert.

18. Suppresed Evidence
Occurs when the arguer ignores important evidence that requires a different conclusion.

Example: Most dogs are friendly and pose no threat to people who pet them. Therefore, it would be safe to pet the little dog that is approaching us now.

*if the arguer ignores the fact that the little dog is excited and foaming in the mouth, then the argument commits the suppressed evidence fallacy

Fallacies of Weak Induction

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Fallacies of weak induction occurnot beacuse the premise are logically irrelevant to the conclusion as is the case with the eight fallacies of relevance, but because the connection between the premise and conclusion is not strong enough to support the conslusion. They often involve emotional grounds for believing the conclusion.

9. Appeal to Unqualified Authority (Argumentum as Verecundiam)
This fallacy is a variety of the argument from authority and occurs when the cited authority or witness lacks credibility. There are 3 areas where discredibilty might occur (1) no expertise, (2) misplace authority, and (3) overlooking biased

Example:
Dr. Bradshaw, our family physician, has stated that the creation of muonic atoms of deterium and tritium hold the key to producing a sustained nuclear fusion reaction at room temp. In view of Dr. Bradshaw's expertise as a physician, we must conclude that this is indeed true.

10. Appeal to Ignorance
When the premise of an argument state that nothing has been proved one way or the other about something, and the conclusion then makes a definite assertion, about that thing, then the argument comits an appeal to ignorance.

Example:
People have been trying for centuries to disprove the claims of astrology, and no one has ever succeeded. Therefore, we must conclude that the claims of astrology are true.

11. Hasty Genralization (Converse Accident)
This fallacy affects inductive generalizations. It occurs when there is a resonable likelihood that the sample is not a representative of the group. Such likelihood may arise if the sample is too small or not randomly selected

Example:
Ten Arab funfamentalist hijacked planes and crashed them into the World Trade Center in NYC. The message is clear: Arabs are nothing but a pack of relogious fanatics prone to viloence.

12.False Cause
Occurs whenever the link between premises and conclusion depends on some imagined causal connection that probably does not exist. It has 4 types of fallacy.

a. Post hoc ergo propter hoc ("after this, therefore account of this")
Presupposes that just because one event preceded another event the first event causes the second event.

b. Non cause procause ("not the cause for the cause")
Committed when what is taken ot be the cause of something is not really the cause at all and the mistake is based on something other than more temporal succeession.

c. Oversimplified cause
Occurs when a multitude of causes is responsible for a certain effect but the arguer selects just one cause of these causes and represents it as if it were the sole cause.
Example: The quality of education in our grade schools and high schools has been declining for years. Clearly our teachers jsut aren't doing their job these days.

d. Gamblers fallacy
committed whenever the conclusion of an argument depends on the suppostion that independent events in a game of chance are causally related.
Example: A fair coin was flipped in a row and each time it came up heads. Therefore, it is extremely likely that it will come up tails on the next flip.

13. Slippery Slope
It ocurs when the conclusion of an argument rest upon an alleged chain reaction and there is not sufficient reason to think that the chain reaction will actually take place.

Example:
Immediate steps should be taken to outlaw pornography once and for all. The continued manufacture and sale of pornographic material will almost ceratinly lead to an increase in sex-related crimes such as rape and incest. This in turn will gradually erode the moral fabric of society and result in an increase in crimes of all sorts. Eventually a complete disintegration of law and order will occur, leading in the end to the total collapse of civilization.

14. Weak Analogy
This fallacy is committed when the analogy is not strong enough to support the conclsion that is drawn.

Example: Harper's new car is bright blue, has leather upholstery, and gets excellent gas mileage. Crowley's new car is also bright blue and has leather upholstery. Therefore it probably gets excellent gas mileage too.

Fallacies of Relevance

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A fallacy of relevance is commited when a premise is logically irrelevant to the conlcusion. It means that the premise does not follow the conclusion. The premises might appear psychologically relevant so the conclusion may seem to follow from the premise, even though it does not follow logically. There are 22 fallacies of relevance.

1. Appeal to Force (Argumentum ad Baculum: Appeal to the "Stick")
This fallacy occurs when an arguer poses a conclusion to another person and tells that person either implicity or explicity that some harm will come to him or her if he or she does not accept the conclusion. Always involves a threat by the arguer to the physical or psychological well being of the listener. The threat opposed is logically irrelevant to the subject matter of the conclusion.

Example:
"Teletubies" is the best show on TV; and if you dont believe it, I am going to call my big brother over here and he is going to beat you up.

2. Appeal to Pity (Argumentum ad Misericordiam)
It occurs when an arguer attempts to support a conclusion by merely evoking pity from the reader or listener.

Example:
Your Honor, I admit that I declared 13 children as dependents on my tax return even though I have only two. But if you find me guilty of tax evasion, my reputation will be ruined. I'll probably loose my job, my poor wife will not be able to have the operation that she desperately needs, and my kids will starve. Surely I am not guilty.

The premises provided by the person is not relevant to the conclusion "Surely I am not guilty" even though it is psychologically relevant.

3. Appeal to the People (Argumentun ad Populum)
This fallacy uses desires to get the reader or listener to accept the conlcusion. There are 2 approaches involve, direct and indirect.

a. Mob Mentality (Direct approach): When an arguer addressing a large group of people, excites the emotions and enthusiam of the crowd.

b. Bandwagon (indirect approach): Plays the desire to fit in
Example: Of course you want to buy Zing toothpaste. Why, 90% of America brushes with Zing.

c. Vanity(indirect approach): often associates the product with someone who is admired, pursued, or imitated, the idea is that you, too will be admired and pursued if you use it.
Exampple: The Few, the Proud, the Marines.

d. Snobbery (indirect approach): It deals with the same association of vanity but it plays a desire to stand out:
Example: A Roll-Royce is not for everyone. If you qualify as one of the select few, this distinguished classic may be seen and driven at Bristish Motor Cars, Ltd.

4. Argument against the person (Argumentum ad Hominem)
This involves 2 arguers. One of them advances (either directly or implicitly) a certain argument, and the other then responds by directing his or her attention not to the person's argument but the person himself. There are 3 types of ad Hominem.

a. Ad Hominem Abusive: the second person responds back the the first persons argument by verbal abuse
Example: Before he died, poet Allen Ginsberg argued in favor of legalizing pornography. But Ginsberg's arguments are nothign but trash. Ginsberg was a marijuana-smoking homosexual and thoughgoing advocate of the drug culture.

b. Ad Hominem Circumstantial: dismissing the arguments on the grounds that the arguer only makes it because of his circumstances or because he stands to benefit if its true.
Example: The Dalai Lama argues that China has no business in Tibet and that the West should do something about it. But the Dalai Lama just wants the Chinese to leave so he can return as leader. Naturally he argues this way. Therefore, we should reject his arguments.

c. Tu Quoque: dismissing or rejecting an argument on the grounds that the arguer is a hypocrite.
Example: Your argument that I should stop stealing candy from the candy store is no good. You tol me yourself just a week ago that you, too, stole candy when you were a kid.

5. Accident
This fallacy is committed when a general rule is applied to a specific case i twas not intended to be; treating a general rule as if it was absolute.

Example:
Freedom of speech is constitutionally guaranteed right. Therefore, John Q. Radical should not be arrested for his speech that incited the riot last week.

6. Straw Man
It is committed when an arguer distorts an opponents argument for the purpose of more easily attacking it. Twisting someones position or argument so tha tit sounds ridiculous.

Example:
Mr. Goldberg has argued against the prayer in public schools. Obviously he advocates atheism. But atheism is what they use to have Russia. Atheism leads to the suppression o fall regions and the replacement of God by an omnipotent state. Is that what we want for this country? I hardly think so. Clearly My. Goldberg's argument is nonsense.

7. Missing the Point
This fallacy iilustrates a special from of irrelevance. It occurs when the premises of a n argument support one particular conclusion, but then a diffrent conclusion, often vaguely related to the correct conclusion is drawn.

Example:
Abuse of the welfare system is rampant nowwdays. Our only altenative is to abolish the system altogether.

8. Red Herring
This fallacy is committed when the arguer diverts the attention of the reader or listener bu changing the subject to a different but sometimes subltly related one.

Example:
There is a good deal of talk these days about pesticides from our fruits and vegetables. But many of these foods are essential to our health. Carrots are an excellent source of vitamin A, brocolli is rich in iron, and orange and grapefruits have lots of vitamin C.