Modes of reasoning Questions 3
lazy808
Lecture15FallaciesofIrrelevance.ppt“Reasoning About Social Issues”
Petrenko Anton, PhD
Hours: By appointment (Monday 11:30-12:30)
E-Mail: [email protected]
AP/MODR1730 D
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This lecture will introduce students to fallacies in argumentation. This lecture will focus on fallacies (of irrelevance) with irrelevant premises.
Lecture Objectives
Ad hominem
Genetic Fallacy
Appeal to force/threat
Appeal to popular sentiment
Appeal to emotion
Straw man
Appeal to Ignorance
Equivocation
Red herring
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Irrelevant Premises: Ad hominem
The fallacy of appeal to the person (ad hominem means ‘to the man’) is when one argues to reject the claim by criticizing the person who makes the claim rather than the claim itself.
Example:
You can’t believe anything Beachemin says about federalism because she is a known separatist.
…because she is gay, or feminist, or has socialist friends…
What Beachemin says about
federalism is not true
Beachemin is a separatist
Who or what a person is (their life choices or beliefs) are irrelevant to the strength or weakness of their arguments. Any person can make a strong argument.
This is a variety of fallacy against the person. It attacks the inconsistency or person’s relationship to the claim: “Ellen claims smoking is bad, but she smokes. So smoking is not bad.” (Whether she smokes is irrelevant to the conclusion that smoking is bad)
Tu quoque (hypocrisy/circumstance)
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Irrelevant Premises: Genetic Fallacy
The genetic fallacy is committed when one argues that a claim is true or false solely because of its origin. (It is close to ad hominem, but does not involve attacking the character or circumstances of the person)
Of course he would say don’t raise taxes. He is rich. So, his claims are untrue.
… (or he is a liberal, or conservative, or mason)
Helen is of a European descent
Helen’s views on Aboriginal rights are not true
Example:
Poisoning the well (discredit the source)
Another fallacy, called poisoning the well is similar to genetic fallacy. The person tries to undermine the point by discrediting the source even before the claim is made.
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Irrelevant Premises: Appeal to force/threat
Fallacy of appeal to force is committed when some kind of force or (threat of) violence is used to bring about the acceptance of the view.
Say that you like me bossing you around, or…
If I was out of bounds, then I will take my ball and go home
I was not out of bounds
Example:
In appeal to force, the premises are irrelevant to the conclusion.
For example: “Either I am right, or else you don’t get to use my car.” The question at issue is if the person is right or not, the threat use force is not relevant to that question (although can be influential).
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Irrelevant Premises: Appeal to popular sentiment
The fallacy of appeal to popular sentiment is committed when one argues that the claim is true or acceptable because some group feels or thinks it is so.
Most people approve of the government’s decision not to pay for in vitro fertilization treatments.
So, this is the correct decision.
Example:
The opinion of the majority is not in itself a reason for the truth of the conclusion (e.g. “most people believe the earth is flat, so the earth is flat”). If the majority have a good reason to hold a view, one should appeal directly to that reason.
Appeal to tradition
Appeal to common practice
The same goes for a common practice or tradition:
“Everyone jumps off the bridge, so we should jump off the bridge”
“Its OK if I speed, everyone does it”
“Its traditional to burn witches, we should burn us some witches”
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Irrelevant Premises: Appeal to emotion
The fallacy of appeal to emotion is made when one uses the arousal of emotion to persuade someone to accept a particular claim.
If the client is convicted, his children will be homeless.
His parents will be devastated.
The client is innocent
Example:
Our sewing machine is made in America, by Americans
Our sewing machine is well-made
Appeal to emotions (pity, fear, anger, indignation, feelings of patriotism and nationalism) are often effective, but they are not relevant to the truth of the claim. This can be similar to the fallacy of popular sentiment:
Doubting the rationale for war means hating America
There is no doubt about the reason for the war
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Irrelevant Premises: Straw man
The straw man fallacy is committed when one distorts a position (argument or a view) so that it can be easily knocked down or refuted.
“David thinks gay relationships deserve special treatment .
He thinks gay lifestyle should be celebrated and promoted.
He wants to turn heterosexuals into a minority”
Dave’s view in favor of gay marriage is incorrect.
Let’s say David is in favor of gay marriage. Then one could construct this straw man argument against him.
Straw man fallacy involves making a caricature (reinterpreting or spinning) of someone’s argument to make it weaker:
“The opposition voted against the plan to increase defense spending for the Canadian military. Why does the opposition want to leave Canada defenseless? Opposition want to make Canada unable to defend its borders.”
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Irrelevant Premises: Appeal to Ignorance
Appeal to ignorance reverses the burden of proof: it asserts some claim, and then challenges you to disprove it. But in the absence of any evidence one should suspend judgement.
The fallacy of appeal to ignorance is committed when one argues that the absence of evidence for a claim must be counted as evidence for it. (or the other way around: absence of evidence is evidence against it)
Science has not proven that God does not exist.
Therefore, God exists
No one has successfully proven that God exists
Therefore, God does not exists
Lack of evidence against a claim does not give a reason to believe the claim.
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Language and Meaning
Nothing is taller than the Empire State Building
Anything is taller than nothing.
Anything is taller than the Empire State Building
Remember this?
Can you paraphrase it and check validity with Venn and traditional method?
Illicit Inclusion
The word ‘nothing’ is used each time with different meaning. Premise 1: it is a quantifier; Premise 2: it is a term (part of the simple sentence. But when we read the sentences, we think the word is used in the same way (we equivocate!).
Things
T
Things taller than ESB
E
Things taller than nothing
N
No things are things taller than ESB
All things are things taller than nothing
All things are taller than ESB
No Ts are Es
All Ts are Ns
All Ts are E
E
A
A
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Irrelevant Premises: Equivocation
The fallacy of equivocation is committed when one uses a word in two different senses in an argument to lead to a misleading conclusion.
The end of everything is perfection
The end of life is death
Therefore, death is the perfection of life
Here “end” means the last in a sequence.
Here “end” means the goal or purpose.
In categorical logic, they would be different sets, but because they sound the same you can make the mistake of treating them as one.
Laws can be only given by law-givers
There are many laws of nature
Therefore, there must be a law-giver: God
Only man is rational
No women is a man
Therefore, no women is rational
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Irrelevant Premises: Red herring
The fallacy of red herring is committed when one brings up an irrelevant issue as a distraction to confuse or sidetrack the main issue.
Canada needs tougher immigration policy. I’ve got a neighbor who says we should let in more immigrants. The 60s… boy, what a great time it was for druggies and wakos! You should see the way the hippies dressed. I guess the guy does not get that the 60s are over.
The term red herring came from the practice of training hounds to follow the correct scent. Red herring was dragged in front of them to distract them from the smell of the fox.
Red herring is an irrelevant distraction in argumentation.
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Irrelevant Premises: Composition/Division
The fallacy of composition is committed when one argues that what is true of the parts must be true of the whole.
The fallacy of division is committed is when one argues that what is true of the whole must be true of the parts. It’s the flipside of composition.
Every part of the bike is lightweight
Therefore, the whole bike is lightweight
Example:
The error here is to think that the characteristics of the part are transferred to the whole. This is not always the case:
“Average small investor puts 2,000 $ in stock; average large investor puts 100,000$. Large investors on the whole invest more into the economy than small investors” (But there could be much more small investors than large ones)
“University students study every conceivable subject. So that university student over there also studies every conceivable subject.”
“This machine is heavy. So every part of it is heavy”
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