Download Fallacies - chass.utoronto

Fallacies
•
•
A fallacy is a mistake in argument.
A fallacy is a mistake in reasoning.
•
A fallacy has been committed when a plausible argument has been offered but it
fails to satisfy the conditions of valid argument or correct inference.
– In other words, when an argument fails to satisfy the ARG conditions, a fallacy
has been committed.
•
•
Fallacies are defects in argument that mislead or misdirect.
If a fallacy is intentional, then it is called a sophism.
•
Some fallacies are so common we give them names.
– That is, we have names for different ways in which the ARG conditions are not
satisfied.
– These names help us communicate the specific problems with an argument.
Amaze and annoy your friends …
• The term “fallacy” is on of the most abused terms in
our language.
– Fallacies are sometimes attributed to people.
• E.g., “Chris is fallacious.”
– “Fallacy” is often used as a synonym for “erroneous”.
• E.g., “It’s a fallacy that it’s sunny!”
• Fallacies are problems with arguments, NOT
problems with people, facts or (while we are on the
subject) your car.
Two Type of Fallacies:
(i) Formal and (ii) Informal
(i) Formal fallacies – Mistakes in the form or structure of arguments.
– If an argument contains a formal fallacy, then it is invalid.
– Recall: validity and invalidity are terms that apply to deductive arguments.
– We will get to these when we look at Ch
(ii) Informal fallacies
– Informal fallacies are problems with the content of an argument. – Are matters of unclear expression, misuse of language, misstatement of facts, misconception, presupposition.
You already know some basic informal fallacies … • If the premises of an argument fails the acceptability or relevance conditions, then often an informal fallacy has been committed.
– Note: The acceptability and relevance of a premise have everything to do with it’s content.
Three basic fallacies
1) Problematic Premise
2) Hasty Conclusion
3) Irrelevant Reason
Problematic Premise
“No man can be a total feminist because in order to be a total feminist, a man would have to know what it feels like to be discriminated against as a woman, and no man can have that experience.”
• The first premise of the argument is very nearly a truism. • That aside, the second premise is more problematic. – It is not clear that a man cannot have an experience of discrimination that is sufficiently similar to the discrimination experience of a woman that would permit him to be a total feminist.
• This argument has a problematic premise. Problematic Premises
• Premises are problematic when they fail the acceptability conditions.
• We have discussed what makes premises problematic at length:
– Confirmation Bias, Availability Error
– Equivocation, Ambiguity, Vagueness
– Jargon, Euphemism
Fallacies of Irrelevance
Ad Hominen Fallacy Tu quoque
Guilt by Association Straw Man Fallacy Fallacious appeal to popularity; appeal to tradition; appeal to ignorance; appeals to emotion; appeals to force
• Red Herring
•
•
•
•
•
Tu quoque
• The arguer makes his opponent appear hypocritical by pointing out a feature of the person with whom he is arguing.
• “You can’t tell me not to use drugs. You already admitted to me that you woke up on a beach in California after a really long acid trip.”
• Hypocrisy may be a poor character trait, but it is not relevant to the argument.
– Extreme example: An evil murdering tyrant could still offer a cogent argument against being an evil murdering tyrant.
Ad hominem
• When an argument attacks a person’s traints or characteristics rather than a position, an ad hominem has been committed.
– Ad hominem = “against the man/person”
• If an argument attacks a person’s actions or circumstances, then a circumstantial ad hominem has been committed.
• The tu quoque fallacy is another name for a circumstantial ad hominem. – Tu quoque = “and you as well”
Emotion: Pity
• “Please, Professor, you can see that my work deserves a better grade; I’m on academic probation and I was sick when I wrote the test.”
• This is an argument that appeals to pity rather than good reasons. It is a fallacious argument ad misericordiam.
Emotion: Force and Fear
• “Accept my premises, or I’ll hit you.”
• This is an argument that appeals to pity rather than good reasons. It is a fallacious argument ad baculum – appeal to “the stick”.
• Note: When a robber says, “Your money or your life.” This is not an argument ad baculum.
Emotion: (Unsuitable) Authority
• “We can ignore the so‐called problem of global climate change, because Michael Crichton says it isn’t a problem.”
• This is an argument that appeals to an unsuitable authority rather than good reasons. It is a fallacious argument ad verecundiam.
Emotion: Tradition
• “These rules were written by wise men about 1800 years ago, and we have always tried to follow them. Therefore, the rules must be good guides.”
• “Women should stay at home because it’s the role of women care for the household.”
• These are claims that appeal to tradition rather than good reasons. They are fallacious arguments ad antiquitatem.
Emotion: Ignorance
• “This can’t be true because I just can’t believe it’s possible.”
• “The solar system must be younger than one million years because even if the sun were made up of solid coal and oxygen it would have burned up in that time.”
• These are arguments that appeals to tradition rather than good reasons. They are fallacious arguments ad ignorantiam.
• This fallacy is committed whenever it is argued that a claim is true because it has not been proved false, or it is argued that a claim is false because it has not been proved true.
Emotions
• Also beware of fallacious appeals to reward, vanity, ridicule …
• Present neuro‐science shows us that reasoning is not unconnected with the emotions. Brains that have emotional centers disconnected from ratiocinative centers, reason poorly.
• But, this does not mean that reasoning is simply emotion.
• It is not important to be unemotional about what you reason about. By all means, be passionate about your reasoning!
• However, it is important to be unemotive in your reasoning and arguments.
Straw Man
• We accept as a rule of argument that: The position being criticized must actually be the position held.
– You must be as scrupulous about representing others’ arguments as you are about acknowledging the use of others’ ideas.
• Often arguments are misrepresented.
– That is, they are recast so that they are similar but not identical to the argument actually being offered.
– The difference may be simple omission of premises but also may be the inclusion of a crucial weakness.
• Regardless of whether the misrepresentation is by accident or intention, responding to a misrepresentation commits a straw man fallacy.
• “[Criticisms of the nominee] emanates from those who worship at the Shrine of Rote Recall – as though life’s problems were like a big crossword puzzle instead of analytical. That a big collection of miscellaneous facts on every subject under the sun available at the tip of the tongue is not sufficient for success has been well illustrated by a recent occupant of the White House.”
Guilt By Association
• Guilt by association is an indirect ad hominem.
• The (illicit) strategy is to impugn a person’s position by associating their argument with a (supposedly) discreditable individual or group.
• “The Ugly Party favours eugenics. Therefore, eugenics is wrong.” vs. “The Ugly Party favours conservation. Therefore, conservation is wrong.”
Genetic Fallacy [real name]
or, Guilt by Origination [my phrase never used]
• Genetic fallacy: arguing that a claim is true or false solely because of its origin (i.e., who it came from). • Example:
– “Selena’s argument regarding Aboriginal rights is no good because she’s of European descent.”
– The insinuation is that Selena could be biased because of her interests or background perspective.
– But her argument should be judged on its own merits, regardless of where she came from!
• “We should reject that proposal for solving the current welfare mess. It comes straight from the Conservative Party.”
• “Russell’s idea about tax hikes came to him in a dream, so it must be a stupid idea.”
Exceptions
• There are times when the background, character, or history of a speaker can reasonably influence our judgments about claims the speaker makes.
– Testimony from an expert witness in a courtroom is usually given extra credence.
– But testimony from someone with a history of perjury could be discounted. Relevance IN GENERAL
• RELEVANCE is a relation between two pieces of information.
– e.g., between two claims, or between some data and a theory.
• If A is relevant to B then the truth or falsity of A has some bearing on the rational acceptability of B. • Conversely, if A is irrelevant to B, then the truth or falsity of A has no bearing on the rational acceptability of B.
Irrelevant Reason
• “I think that we should take paranormal research seriously. I think that the paranormal is really neat, and the Vampire Diaries is a great TV show.”
• The premises of this argument are not relevant to the conclusion. They provide no support of the conclusion. • The argument commits the fallacy of irrelevant reason, or as it is commonly called, a non sequitur. – From the Latin, meaning “does not follow.”
The Question to Ask Yourself
• If this premise were true, what effect would it have on the rational acceptability of the conclusion?
Positive, negative, and irrelevance
• A is positively relevant to B if the truth of A counts in favor of the truth of B.
• A is negatively relevant to B is the truth of A counts against the truth of B.
• A is irrelevant to B if it is neither positively nor negatively relevant to B. Some Nuances
• Irrelevance is a serious objection, if it can be established. – As we have already noted, non sequitur is the term that you usually apply to arguments flawed by irrelevant premises.
• But, relevance is rarely a yes or no question.
– There are shades of grey and difficult borderline cases.
• Irrelevant premises can nearly always be repaired by adding in unstated premises. – Sometimes things that look blatantly irrelevant should not be treated as irrelevant because unstated premises are involved. – However, this does not mean that every irrelevant premise should be saved by inserting implicit premises.
• One problem is that it is often unclear whether the author is tacitly committed to all the premises that would be required.
Hastiness
Ways to be Hasty
•
•
•
•
Begging the question
Complex questions
False Dichotomy
Slippery Slope
• Fallacy of composition
• Fallacy of division
• Faulty Analogy
Begging the Question
• Begging the question is an abused term.
– It is incorrectly used to describe questions that are invited by, or alluded to by, a line of inquiry or reasoning.
• Begging the question is circular reasoning.
– To beg the question is offer your conclusion as one of your premises.
– Of course, this presupposes the truth of what is at issue. • Also known as a petitio principii, or simply a petitio.
“To allow every man unbounded freedom of speech must always be, on the whole, advantageous to the state; for it is highly conducive to the interests of the community that each individual should enjoy a liberty of expressing his sentiments.”
Richard Whately, Elements of Logic (1862).
Standardized
P1: Unlimited individual liberty of expression is conducive to the interests of the community.
P2: Each individual should enjoy an unlimited liberty to express personal sentiments.
C1: Allowing unlimited liberty of expression must always, on the whole, advantageous to the state.
Hasty Conclusion
“We arrived at the gate at 7:30, and the cashier happily took our money for admission, without any word of warning. As soon as we entered the zoo and walked across the bridge, the loudspeaker announced that the zoo was closing at 8. We asked if we could get a pass for the following day, but the answer was no. In summary, it is easy to see that Calgary is anything but a friendly city, but rather out to take the tourist for all that they can get.” [p.73]
•
The premises of this argument are unacceptable because they insufficient to support the conclusion. – The conclusion has been reached hastily. – This argument commits the fallacy of a hasty conclusion.
Slippery Slope
• The slippery slope fallacy: arguing, without good reasons, that taking a particular step will inevitably lead to a further, undesirable step (or steps). – The idea behind the metaphor is that if you take the first step on a slippery slope, you will have to take others because, well, the slope is slippery. More examples of a slippery slope
• “Oppose increases in tuition! Or next thing you know, tuition will be $20,000 per year!”
• “We must ban all forms of erotica. If we don’t, rape will become as common as jaywalking.”
– In these cases, there is little good reason to think that the feared consequence will follow. Still more slippery‐ness
• But some slippery slope arguments are good:
– “If you have Lyme disease and ignore the symptoms, you could end up with a life‐threatening illness. So see your doctor right now!”
• In evaluating a slippery slope argument, you have to look at the particulars of the case: – Is there really a good reason to think that the outcome would follow?
False Dilemma/Dichotomy
• The fallacy of false dilemma takes two forms:
1. Asserting that there are only two alternatives to consider in some issue when there are actually more than two; or,
2. Asserting that there are two distinct alternatives which in fact may not be mutually exclusive.
• Dilemma: a situation that presents just two—usually unattractive—alternatives.
– “Either wash the dishes or do your homework!”
False Dilemma 1
An example of the first type of false dilemma
• “Look, either you support the war, or you are a traitor to your country. You don’t support the war. So you’re a traitor.”
– This argument only works if there really are only two alternatives. Because this argument does not allow other possibilities, it is fallacious.
False Dilemma 2
An example of the second type of false dilemma
 “Why are you so concerned with the rights of the accused? Do you care about the rights of the accused, or the rights of their victims?”
 In fact, it is possible to be concerned with both. • “The Challenge of our Time: Raise Taxes or Cut Services?”
– Again, maybe we can do both, or maybe there are other alternatives. • Propositional logic shows that “p or q” is the same thing as saying “if not p then q.”
• Thus, false dilemma can also appear in the form of a conditional:
– “If we don’t raise taxes then we have to cut services.”
• Again, there might be other possibilities, such as delivering services more efficiently. The Fallacy of Composition
• The fallacy of composition: arguing that what is true of the parts of something must be true of the whole thing.
• Example:
– “The atoms that make up the human body are invisible. Therefore, the human body is invisible.”
• It is not always fallacious to argue this way:
– “The atoms that make up the human body have mass. Therefore, the human body has mass.”
Category Mistakes
• Fallacy of composition often involves a category mistake:
– “All of the players on the Badgers are great. Therefore, the Badgers are a great team.”
• The sense in which an individual athlete is great is not the sense in which a team is great.
• By contrast, the sense in which an individual atom has mass is the same as the sense in which a body made of atoms has mass. Where it Happens
•
•
Fallacies of composition can occur when we fail to realize that size or total
amount matters:
– “It doesn’t cause a problem if one or two people in the class chat
quietly. So, it won’t cause a problem if everyone chats quietly.”
Sometime people commit the fallacy of composition in statistical
arguments:
– “The average middle class Canadian pays $20,000 per year in income
tax, while the typical high‐income earner pays $100,000 per year in
income tax. Therefore, high income earners pay more income tax in
total.”
– Not necessarily!—because there could be many more middle class
earners than high‐income earners.
The Fallacy of Divsion
• The fallacy of division: arguing that what is true of the whole must be true of the parts.
– It’s the flip side of the fallacy of composition. • Example:
– “This machine is heavy. Therefore, all the parts of this machine are heavy.”
Examples
•
“Since this committee is a powerful force in Canadian politics, each member of the committee is a powerful force in Canadian politics.”
•
“University students (as a group) study every conceivable subject. So that
university student over there also studies every conceivable subject.”
•
Fallacy of division can also take a statistical form:
– “Mike can run faster than Colleen because men on average can run faster than women.”
• This is fallacious, since what is true on average might not be true for individual cases. Faulty Analogy
• An analogy draws a comparison between two things.
– “Breakfast without orange juice is like a day without sunshine!”
• An argument from analogy compares two things, and then suggests they must be alike in some further, less‐obvious, way.
• The fallacy of faulty analogy: when the items being compared are not sufficiently similar in relevant ways. Examples
•
“Dogs are warm‐blooded, nurse their young, and give birth to puppies. Humans are warm‐blooded and nurse their young. Therefore, humans give birth to puppies too.”
– Clearly, humans are not like dogs in all respects!
•
“Doctors are allowed to look up difficult diagnoses in their medical textbooks, so students should be able to look up tough test questions in their texts.”
•
“Whiskers are like wheat, and shaving is like plowing the field. So shaving makes your beard grow faster!”
Uses of Analogy
• One of the great tools of the human mind is the ability to note similarities between apparently different things.
• However, recognition of analogy is a tool of discovery of new facts and concepts, not of logical justification.