Logical Fallacies
Fallacy: A mistake in reasoning; an argument that fails to provide adequate logical support for the truth of its conclusion, yet appears convincing or persuasive in some other way. Common examples include both formal fallacies (structural errors in deductive logic) and informal fallacies (efforts to persuade by non-rational appeals).
1. Accentus
A Fallacy of Ambiguity, where the ambiguity arises from the emphasis (accent) placed on a word or phrase that results in a shift of meaning.
For example, "Joan said that she never wants to see another Demi Moore movie, so we won't show her another one; we'll just play this same one over and over again."
2. Ad Antiquitam
A fallacy of asserting that something is right or good simply because it is old (i.e. tradition); that is, because "that's the way it's always been."
For example, "For thousands of years Christians have believed in Jesus Christ. Christianity must be true, to have persisted so long even in the face of persecution."
Another example includes: "Slavery couldn't have been all that bad or else why did people allow it to go on as long as it did?"
3. Ad Baculum
An argument that resorts to fear via the threat of force and the possibility of punishment for noncompliance to cause the acceptance of the conclusion.
For example, " . . . thus there is ample proof of the truth of the Bible. All those who refuse to accept that truth will burn in Hell."
4. Ad Crumenam
Fallacy of believing that money is a criterion of correctness; that those with money are more likely to be right. This is often due to the psychological tendency to associate the rich and the methods by which they acquired their wealth with intelligence, thus creating the correlation of wealth with sound judgment.
For example, "Microsoft software is undoubtedly superior; why else would Bill Gates have got so rich?"
5. Ad Hominem
Argumentum ad hominem is literally "argument directed at the man" and is an argument that attempts to disprove the truth of what is asserted by attacking the speaker rather than the speaker's arguments. This is invalid because the truth of an assertion does not depend upon the goodness of those asserting it. There are two basic types of ad hominem arguments: (1) abusive and (2) circumstantial.
For example, sometimes in a court of law doubt is cast upon the testimony of a witness by showing, for example, that he is a known perjurer. This is a valid way of reducing the credibility of the testimony given by the witness, and not argumentum ad hominem; however, it does not demonstrate that the witness's testimony is false.
This logical fallacy is more easily understood in the following Ad Hominem argument: "You're wearing pants! But Hitler wore pants too!"
6. Ad Ignorantiam
An argument that a proposition is true because it has not been shown to be false, or vice versa. Ad ignorantium arguments are also known as "appeals to ignorance." This fallacy has two forms:
1. P is true, because it has not been proven false.
2. P is false, because it has not been proven true.
For example, "Of course telepathy and other psychic phenomena do not exist. Nobody has shown any proof that they are real."
7. Ad Lazarum
A fallacy of assuming that because someone is poor, he or she is sounder or more virtuous than one who is wealthier. This fallacy is the opposite of the informal fallacy "argumentum ad crumenam." In Western society, this misconception finds its genesis in the Christian tradition, "It is easier for a camel to go through the eye of a needle, than for a rich man to enter the kingdom of God,"
For example, "That homeless man must be smart, he doesn't have anything else to do but think."
8. Ad Misericordiam
An argument that appeals to pity for the sake of getting a conclusion accepted.
For example, "I did not murder my mother and father with an axe. Please don't find me guilty; I'm suffering enough through being an orphan."
9. Ad Nauseam
The incorrect belief that an assertion is more likely to be true the more often it is heard. An "argumentum ad nauseum" is one that employs constant repetition in asserting a supposed truth.
10. Ad Novitam
A fallacy of asserting that something is more correct (or of better quality) simply because it is new or newer than something else. This type of fallacy is the opposite of the "argumentum ad antiquitam" fallacy.
For example, "The new version of Psycho is better than the Hitchcock one because it is in color."
11. Ad Numeram
This fallacy is closely related to the argumentum ad populum. It consists of asserting that the more people who support or believe a proposition, the more likely it is that that proposition is correct.
Examples include the Salem Witchcraft trials, slavery, McCarthyism, and Nazism.
12. Ad Populum
An argument that appeals to the beliefs of the multitude (i.e., the "populace"). Oftentimes, the speaker deals with the passions of the audience rather than with salient issues. This fallacy is also known as an "Appeal to Tradition/the Gallery/the People." Ad populum arguments often occur in (1) propaganda, (2) demagoguery, and (3) advertising.
For example, "Nixon was a good president, otherwise, why did so many Americans vote him into office?"
13. Ad Verecundiam
An argument in which an authority is appealed to on matters outside his or her field of authority.
For example, "Einstein was a genius and he believed in God."
Einstein's field of specialization was quantum physics, not theology. This fallacy operates upon the belief that because someone is knowledgeable in one field, he or she is a scholar in all fields.
14. Affirmation of the Consequent
An argument from the truth of a hypothetical statement, and the truth of the consequent to the truth of the antecedent. In the syllogism below, P is the antecedent and Q is the consequent:
P implies Q
Q is true (Affirming the consequent)
______________
Therefore: P is true
For example, "If Dole had been elected President in 1996, then he would no longer be a Senator. Dole is no longer a Senator. Therefore, Dole was elected President in 1996."
15. Ambiguity
An argument in the course of which at least one term is used in different senses. Many people who are not effective in expressing themselves fall prey to this logical fallacy because they do not specify the topic they are addressing and leave their audience to "figure it out" or assume "they [the audience] get what I'm saying" or are unaware there are other interpretations of the term they are implementing. Also, many people will take another person's words "out of context," using this form of logical interpretation in order to invalidate another's argument.
For example, the phrase "I'll give you a ring tomorrow" could signify either the promise of a gift of jewelry or merely an intention to telephone.
Another example includes "Each dealer or exhibitor shall have an attending veterinarian who shall provide adequate veterinary care to its animals in compliance with this section."
In the latter example, the term "adequate" is not specific enough and may be interpreted to one's advantage.
16. Amphiboly
Amphiboly is a syntactic error. The fallacy is caused by faulty sentence structure and can result in a meaning not intended by the author. Amphiboly occurs when the premises used in an argument are ambiguous because of careless or ungrammatical phrasing.
For example, "One morning in Africa, Captain Spaulding shot an elephant in his pajamas. Therefore, it is dangerous for elephants to be caught wearing pajamas early in the morning."
17. Bifurcation
Also referred to as the "black and white" fallacy, bifurcation is the presentation of a situation or condition with only two alternatives, whereas in fact other alternatives exist or can exist.
For example, if a person states that it is not cold today, that does not mean it is necessarily hot.
18. Burden of Proof
Shifting the burden of proof, a special case of "argumentum ad ignorantium," is a fallacy of putting the burden of proof on the person who denies or questions the assertion being made. The source of the fallacy is the assumption that something is true unless proven otherwise.
For example, "Okay, so if you don't think the gray aliens have gained control of the US government, can you prove it?"
19. Circulus in Probando/Circulus in Demonstrando
Reasoning that improperly assumes the truth of what is at issue. Otherwise known as a circular argument (circular reasoning), it implicitly employs its own conclusion as a premise. A circular definition defines an expression in terms of itself. The problem is that circular reasoning—however accurate—is bound to be uninformative.
For example, "We know that God exists because the Bible tells us so. We know that the Bible is true because it is the word of God."
20. Composition
An argument in which one assumes that a whole has a property solely because its various parts have that property. Fallacy of Composition is a type of Fallacy of Ambiguity.
For example, "Each of the elements Sodium Chloride (NaCl) is poisonous to human beings; therefore, this compound is itself poisonous to human beings."
Sodium Chloride is commonly known as table salt.
21. Converting a Conditional
If P then Q, therefore, if Q then P.
For example, "Birds are animals then animals are birds."
The statement thus implies an absolute that all animals are birds as a consequence.
22. Cum Hoc, Ergo Propter Hoc
A fallacy of correlation that links events because they occur simultaneously; one asserts that because two events occur together they are causally related, and leaves no room for other factors that may be the cause(s) of the events. This fallacy is similar to the "post hoc, ergo propter hoc" fallacy.
For example, "Literacy rates have steadily declined since the advent of television. Clearly television viewing impedes learning."
Other factors that could be factors in the declining literacy rate due this time could include poor educational funding, increased birth rates (such as during the Baby Boomer period in America) where parents are not able to devote as much time to each child if there were fewer offspring, etc.
23. Denial of the Antecedent
This fallacy is an argument of the form "A implies B, A is false, therefore B is false." Again, the truth table for implication makes it clear why this is a fallacy.
Note that this fallacy is different from Non Causa Pro Causa; the latter has the form "A implies B, A is false, therefore B is false", where A does not in fact imply B at all. Here, the problem is not that the implication is invalid; rather it is that the falseness of A does not allow us to deduce anything about B.
P implies Q
Not-P (Denial of Antecedent)
____________
Therefore: Not-Q
For example, "If Fluffy is a cat, then a Fluffy is a mammal. But Fluffy is not a cat. Therefore, Fluffy is not a mammal."
Fluffy could easy be a hamster.
24. Dicto Simpliciter
Dicto Simpliciter (also known as "Sweeping Generalization") occurs when a general rule is applied to a particular situation in which the features of that particular situation render the rule inapplicable.
For example, "Christians generally dislike atheists. You are a Christian, so you must dislike atheists."
The person in question could be impartial to an atheist's theological perspectives.
25. Division
An argument in which one assumes that various parts have a property solely because the whole has that same property. Fallacy of Division is a type of Fallacy of Ambiguity.
The fallacy of division is the opposite of the fallacy of composition. Like its opposite, it exists in two varieties. The first is to assume that a property of some thing must apply to its parts.
For example, "You are studying at a rich college. Therefore you must be rich."
The person could be going to the "rich college" on a scholarship.
The other is to assume that a property of a collection of items is shared by each item.
For example, "Ants can destroy a tree. Therefore this ant can destroy a tree."
Obviously, a single ant could not destroy a tree by itself. It must be part of the group which has been show to collectively exhibit that property (or ability).
More exactingly, this is the informal fallacy of attributing some feature of a collection to the members of that collection individually, or reasoning from whole to part.
26. Equivocation
Equivocal means (1) of uncertain significance; not determined, and (2) having different meanings equally possible. Equivocation is a type of Fallacy of Ambiguity. The opposite of equivocation is "unovocation," in which a word always carries the same meaning through a given context. Equivocation is an argument in which an equivocal expression is used in one sense in one premise and in a different sense in another premise ( or in the conclusion). This occurs when a key word is used with two or more different meanings in the same argument.
For example, "Odd things arouse human suspicion. But seventeen is an odd number. Therefore, seventeen arouses human suspicion."
27. False Analogy
An analogy is a partial similarity between the like features of two things or events on which a comparison can be made. A false analogy involves comparing two things that are not similar. Note that the two things may be similar in superficial ways, but not with respect to what is being argued.
For example, "Of course homosexuality is unnatural. When was the last time you saw two animals of the same sex mating?"
Another example includes a popular anti-smoking billboard advertisement: The ad depicts a deer, a duck, a pig, and a dog all with cigarettes in their mouths. The caption reads, "It looks just as stupid when you do it." However, this is a false analogy in that merely because animals do not engage in the same activity, it does not follow that human are incorrect in doing so because, does a deer, a duck, or a dog look "stupid" driving a car? Does that mean that humans should not drive as a result?
28. Ignoratio Elenchi
Ignoratio Elenchi stands for "pure and simple irrelevance." Ignoratio Elenchi is otherwise known as an Irrelevant Conclusion and consists of claiming that an argument supports a particular conclusion when it is actually logically nothing to do with that conclusion.
For example, a Christian may begin by saying that he will argue that the teachings of Christianity are undoubtedly true. If he then argues at length that Christianity is of great help to many people, no matter how well he argues he will not have shown that Christian teachings are true.
29. Illicit Process
Illicit Process is also known as a Complex Question or Interrogation. It is a syllogistic argument in which a term is distributed in the conclusion, but not in the premises. One of the rules for a valid categorical syllogism is that if either term is distributed in the conclusion, then it must be distributed in the premises. There are two types of Illicit Process: Illicit Process of the Major Term and Illicit Process of the Minor Term. This is the Fallacy of Presupposition.
For example, "Where did you hide the money you stole?"
30. Non Causa, Pro Causa
An argument to reject a proposition because of the falsity of some other proposition that seems to be a consequence of the first, but really is not.
For example, "I took an aspirin and prayed to God, and my headache disappeared. So God cured me of the headache."
Obviously the aspirin was one of two factors which could have been the genesis for the person's relief. However, in this case, the individual has conveniently overlooked this aspect of the situation in order to propose an illicit thesis.
31. Non Sequitur
Latin phrase meaning, "It does not follow." An argument in which the conclusion is not a necessary consequence of the premises. A conclusion drawn from premises that provides no logical connection to it.
For example, "Since Egyptians did so much excavation to construct the pyramids, they were well versed in paleontology."
Paleontology has no direct correlation in this sense with excavation in relation to architecture and construction.
32. Petitio Principii
Also known as Begging the Question. An argument that assumes as part of its premises the very conclusion that is supposed to be true. It is a fallacy of assuming at the onset of an argument the very point one is trying to prove. Although arguments of this sort are formally valid because it is impossible for their conclusions to be false if their premises are true, they fail to provide logical support for their conclusions, which have already been accepted without proof at the outset.
Petitio principii has two forms:
1. P is true, because P is true.
2. P is true, because A is true.
And A is true because B is true.
And B is true because P is true.
For example, "Since firefighters must be strong men willing to face danger every day, it follows that no woman can be a firefighter."
33. Plurium Interrogationum
Also known as Many Questions. A demand for a simple/single answer to a complex question(s).
For example, "Are higher taxes an impediment to business or not? Yes or no?"
34. Post Hoc, Ergo Propter Hoc
Latin phrase meaning "After this, therefore because of this." Also known as Slippery Slope. An argument from a premise of the form "A preceded B" to a conclusion of the form "A caused B." Simply because one event precedes another event in time does not mean that the first event is the cause of the second event.
For example, "If we legalize marijuana, then we would have to legalize crack and heroin and we'll have a nation full of drug-addicts on welfare. Therefore we cannot legalize marijuana."
35. Quaternio Terminorum
An argument of the syllogistic form in which there occur four or more terms. In a standard categorical syllogism there are only three terms: a subject, a predicate, and a middle term.
For example, "All managers are politicians, and all old men are administrators, so all old men are politicians."
36. Red Herring
A fallacy when irrelevant material is introduced to the issue being discussed, such that the audience's attention is diverted away from the points being made and toward a different conclusion. It is not logically valid to divert a chain of reasoning with extraneous points.
For example, "You may claim that the death penalty is an ineffective deterrent against crime, but what about the victims of crime? How do you think surviving family members feel when they see the man who murdered their son kept in prison at their expense? Is it right that they should pay for their son's murderer to be fed and housed?"
37. Reification
Also known a Hypostatization. To reify something is to convert an abstract concept into a concrete thing. Reification is a Fallacy of Ambiguity.
For example, "I noticed you described him as 'evil'. Where does this 'evil' exist within the brain? You can't show it to me, so I claim it doesn't exist, and no man is 'evil.'"
38. Secundum Quid
Latin for "according to something." Also known as Hasty Generalization. An argument in which a proposition is used as a premise without attention given to some obvious condition that would affect the proposition's application. It is a fallacy that takes evidence from several, possibly unrepresentative, cases to a general rule; generalizing from few to many. Note the relation to statistics: Much of statistics concerns whether or not a sample is representative of a larger population. The larger the sample size, the better the representation.
For example, "Martha Stewart was a corrupt homemaker. Therefore all homemakers are corrupt."
39. Special Pleading
Special pleading is a logical fallacy wherein a double standard is employed by the person making the assertion. Special pleading typically happens when one insists upon less strict treatment for the argument he or she is making than he or she would make when evaluating someone else's arguments.
For example, "If a man never speaks of homosexuality he is in denial and therefore gay. Conversely, if a homosexual never speaks of heterosexuality, it is a sign that he is comfortable with his orientation."
40. Straw Man
A fallacy to misrepresent someone else's position for the purposes of more easily attacking it, knock down that misrepresented position, and then to conclude that the original position has been demolished. It is a fallacy because it fails to deal with the actual arguments that have been made.
For example, "To be an atheist, you have to believe with absolute certainty that there is no God. In order to convince yourself with absolute certainty, you must examine the entire Universe and all the places where God could possibly be. Since you obviously haven't, your position is indefensible."
41. Tu Quoque
Also known as Two Wrongs Make a Right. It is a fallacy because it makes no attempt to deal with the subject under discussion. Such a fallacy is a misplaced appeal to consistency. This is the famous "so do you" fallacy. It occurs when an action is argued to be acceptable because the other party has performed it. The informal fallacy of replying to criticism by arguing that one's opponent is guilty of something equally improper.
For instance, "You're yelling at me."
"So? You've been been yelling at me too."
42. Undistributed Middle
A syllogistic argument in which the middle term of a categorical syllogism is not distributed in at least one of the premises.
For example, "All dogs are mammals. Some mammals are whales. Therefore, some dogs are whales."