Most of the following fallacies were discussed in the logic overview chapter. Asterisks below indicate new ones that do not appear there.
FALLACIES OF RELEVANCE
Fallacies of relevance occur when the premises of an argument have no bearing upon its conclusion. In addition, such fallacies often involve a distractive element which diverts attention away from this very problem. These are often called non sequiturs (from the Latin phrase meaning "it does not follow")
1. Ad hominem abusive (against the person, abusive): attempt to refute a claim by attacking a person's age, character, family, gender, ethnicity, social or economic status, personality, appearance, dress, behavior. or professional, political, or religious affiliations.
Example: Jones advocates fluoridation of the city water supply; jones is a convicted thief; therefore, we should not fluoridate the city water supply.
Example: The Beatles aren’t a great band, since they continually took recreational drug.
*2. Ad hominem circumstantial (against the person, vested interest): attempt to refute a claim by arguing that its proponents are motivated a vested interest, that is, by the desire to gain something or avoid losing something. This fallacy is often introduced by phrases such as: "Of course, that's what you'd expect them to say."
Example: Jones supports the fluoridation bill pending in Congress; he does so because he owns a major fluoridation firm, which will reap huge dividends if the bill passes; therefore, we should not support this bill.
Example: Of course you’d say the Beatles are a great band since you’re the president of the Beatles Fan Club.
*3. Ad hominem double standard (against the person, tu quoque “you too”): the attempt to refute a claim by attacking its proponent on the grounds that he or she is a hypocrite, upholds a double standard of conduct, or is selective and therefore inconsistent in enforcing a principle.
Example: Jones advocates fluoridation of the city water supply; Jones himself avoids drinking fluoridated water; therefore, we should not fluoridate the city water supply.
Example: No, the Beatles aren’t a great band, since you yourself don’t even own any of their albums.
4. Straw man: attempt to refute a claim by confusing it with a less plausible claim (the straw man) and then attacking that less plausible claim instead of addressing the original issue.
Example: There can be no truth if everything is relative; therefore, Einstein's theory of relativity cannot be true.
Example: The position of the democrats is wrong since democrats are essentially socialists.
5. Appeal to force (ad baculum): the attempt to establish a conclusion by threat or intimidation.
Example: You should vote for me since if you don’t, I'll tell everyone about your drug problem.
Example: You should volunteer to work this weekend, since I can have you replaced if you don’t.
6. Appeal to authority (ad verecundiam): we accept (or reject) a claim merely because of the prestige, status, or respect we accord its proponents (or opponents).
Example: My teacher says that I should be proud to be an American; therefore, I should be proud to be an American
Example: President Zucchini says our country is God’s chosen nation, so it must be true.
7. Appeal to the masses (ad populum): we infer a conclusion merely on the grounds that most people accept it.
Example: Everybody believes that euthanasia is wrong; therefore, euthanasia is wrong.
Example: Nobody is a better judge than public opinion.
Example: Most people eat meat; shouldn’t you? (Bandwagon effect: we are asked to join forces with others)
8. Appeal to pity (ad misericordiam): we are asked to excuse or forgive an action on the grounds of extenuating circumstances.
Example: Officer, you shouldn’t give me a ticket since I was buying candy for my crying baby.
Example: Yes, I know my dog knocked over your garbage can, but just look at big sad eyes.
9. Appeal to ignorance (ad ignorantiam): X has not been proved, therefore x is false.
Example: No one has ever proved that God does not exist, therefore, God exists.
Example: Hire me for the job; why shouldn’t you?
9. Red herring (changing the subject): an extraneous or tangential matter used purely to divert attention away from the issue posed by the argument.
Example: Some members of the police force may be corrupt, but there are corrupt politicians, corrupt plumbers, etc.
Example: Yes, I did say that the Ford Focus an untrustworthy piece of junk, but I went ahead and bought it because it was on sale.
10. Irrelevant conclusion (missing the point; ignoratio elenchi): the premises of an argument warrant a different conclusion from the one that the arguer draws. Technically, all of the fallacies in this section involve irrelevant conclusions. But this specific fallacy of “irrelevant conclusion” is a very general one, and it applies when an argument does not fit any of the more specific patterns of irrelevance above.
Example: Unemployment is a very serious problem; therefore, we should support the senate bill to eliminate the death tax.
Example: Abortion is wrong; therefore we should abolish capital punishment.
FALLACIES OF CIRCULAR REASONING
1. Circular reasoning (begging the question and petition principia): assuming what we are trying to prove (assumes its own conclusion).
Example: “The world, I found, admired the philosopher, because good judges did so; and good judges admired him, because all the world did it.” (James Beattie, “Castle of Scepticism”)
Example: “We know that thou art a teacher come from God; for no man can do these signs that thou doest, except God be with him.” (John 3.2).
*2. Question-begging epithet: phrases that prejudice discussion and assume the very point at issue.
Example: John is a bleeding-heart liberal, so he cares more about others than he does himself.
Example: John is a Neanderthal conservative, so he cares about himself more than he does others.
*3. Complex question (loaded question): presupposing an answer to a logically prior question.
Example: Have you stopped torturing your cat?
Example: Are you going to publicly announce that you’re in love with your business partner’s wife?
FALLACIES OF LANGUAGE (sematic fallacies)
Fallacies of language result when the language employed to construct arguments has multiple meanings or is excessively vague in a way that interferes with assessment of the argument.
1. Equivocation (ambiguity): the meaning of an expression shifts during the course of an argument.
Example: It is silly to fight over mere words; discrimination is just a word; therefore, it is silly to fight over discrimination
Example: Necessity is the mother of invention; bread is a necessity; therefore, bread is the mother of invention.
Example: What is necessary is good; evil is necessary; therefore, evil is good.
Example: No human being is made of paper. All pages are human beings. Therefore, no pages are made of paper.
*2. Amphiboly: arguments whose meanings are indeterminate because of loose or awkward sentence construction.
Example: “Charles the First walked and talked, thirty minutes after he had his head chopped off.”
Example: For Sale, a Newfoundland dog; will eat anything, particularly fond of children.
Example: Wanted, a piano by a young lady made of mahogany.
Example: I hope that you the enemy may slay.
*3. Accent: emphases that generate multiple and often misleading interpretations.
Example: I’m in favor of a missile defense system that effectively defends America.
Example: John turned his homework in on time today; therefore, John usually turns his homework in late.
Inductive fallacies occur when the probability of an argument's conclusion is low, or at least less than the arguer supposes.
*1. Accident (destroying the exception): ignoring exceptions to a rule. Fallaciously moves from a general statement to a particular.
Example: Praying is superstitious; therefore, praying before the presidential inauguration is superstitious.
Example: Reason is only found in human form; therefore, if rational gods and aliens exist, they must be in human form.
*2. Hasty generalizations (converse-accident): fallaciously inferring a conclusion about an entire class of things from inadequate knowledge of some of its members. Fallaciously moves from particular statements to a general statement
Example: Last Monday I wrecked my car; the Monday before that my furnace broke; therefore, bad things always happen to me on Mondays.
Example: All of the guitar players I know own Fender Stratocasters, so they must be the most popular guitar.
*3. Slippery slope (misuse of “if-then”): the conclusion of an argument rests upon an alleged chain reaction, suggesting that a single step will result in an undesirable outcome. This fallacy often involves a chain of hasty generalizations.
Example: Caffeine use leads to cocaine use, which leads to crack use; therefore, you shouldn’t take caffeine.
Example: College teaches multiculturalism, which leads to questioning values, which leads to rejecting religion.
4. False analogy: comparing things in an analogy that are too dissimilar.
Example: The American colonies justly fought for their independence in 1776; today the American Football Alliance is fighting for its independence; therefore, the Alliance’s cause is also just.
Example: Because human bodies become less active as they grow older, it is reasonable to expect that political bodies will also become less active the longer they are in existence.
*5. Gambler’s fallacy: the gambler falsely assumes that the history of outcomes will affect future outcomes.
Example: Heads has come up heads five times in a row now, so there is a greater than 50/50 chance that tails will come up on the next toss.
Example: Since it has rained three days in a row, and it can’t rain forever, I think we can count on having a sunny day tomorrow.
6. False Cause (post hoc ergo propter hoc – “after this, therefore because of this”): confusing a cause with an effect; inferring a causal connection based on mere correlation.
Example: We never had a problem with this photocopier until you were hired.
Example: Her business was booming until she stopped going to church.
*7. Suppressed evidence (cherry picking the evidence): intentionally failing to use information suspected of being relevant and significant.
Example: This is the highest-rated printer; therefore, it is the best choice for us (suppressing the fact that it costs three times more than competing brands)
Example: Leaded gasoline works better in engines than unleaded, therefore the best thing for the country would be to move back to leaded gasoline.
Formal fallacies occur when they follow a rule which is demonstrably invalid, commit a category mistake, or misuse a logical connective.
1. Denying the antecedent (fallacious modus tollens): denying the antecedent of an if-then statement, and then inferring that the consequent must also be denied.
Example: If it rains, the sidewalk will be wet; it’s not raining; therefore, the sidewalk is not wet.
Example: If you stub your toe, you’ll have a hard time walking; you didn’t stub your toe; therefore, you won’t have a hard time walking.
2. Affirming the consequent (fallacious modus ponens): affirming the consequent in an if-then statement, and then inferring that the antecedent is true.
Example: If it rains, the sidewalk will be wet; the sidewalk is wet; therefore, it must be raining.
Example: If you stub your toe, you’ll have a hard time walking; you have a hard time walking, therefore you stubbed your toe.
3. Composition: invalidly imputing characteristics of one or more parts of a thing to the whole of which they are parts.
Example: Every sentence in this book is well written, therefore this book is well written.
Example: All the pixels in this computer screen are red, green and blue, therefore the only colors that this computer screen displays are red, green and blue.
4. Division: invalidly imputing characteristics of the parts to the whole to the parts.
Example: This book is written in English, therefore, every sentence in this book is in English.
Example: This company is immoral, so everyone who works for it is immoral.
*5. Excluded middle (false dichotomy, misuse of “or”): making a false assumption that only one of a number of alternatives holds.
Example: Either you’re for us or you’re against us; you’re not for us; therefore, you must be against us.
Example: You’ll either go to heaven or to hell, and why would you want to gamble on going to hell?