Logical Fallacies
Arguments
• Claim: The position being argued
• Reasons: Support for the claim
• Warrants: The principle or chain of reasoning that connects
the reason to the claim
• We need to connect claims to reasons with logical warrants
for arguments to be sound.
What are logical fallacies?
• Mistakes in our reasoning
• Claims, warrants, or pieces of evidence are invalid, insufficient, or
disconnected
• Seriously affect our ability to argue effectively
• Sometimes we think that our faulty argument is sound
• Sometimes we think a flawed argument will win us the battle
• Sometimes these are difficult to spot because they are
disguised by the skillful use of words or images.
Fallacies
• Ad Hominem—Against the Man
• Avoiding the issue by attacking a person’s character
• Used to divert an audience’s attention from the issue at hand
• A prosecutor asks the judge to not admit the testimony of a burglar
because burglars are not trustworthy.
• Begging the Question
• Circular Reasoning
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Drawing conclusions from assumptions that have not been proven
CLAIM: You can’t give me a C in this course…
REASON: …because I am an A student.
WARRANT: An A student is someone who can’t receive Cs.
Fallacies
• Either/Or Fallacy
• Contrasting your own choice only with one that is completely
undesirable; Overlooking other options
• All drugs should be either legalized or banned completely. (Ignores
other positions like legalizing marijuana for cancer treatments but
not for general use)
• Equivocation
• Using a word with two or more definitions, usually in order to
confuse or deceive
• Macbeth has nothing to worry about “till Birnam wood / Do come to
Dunsinane” –how can a forest move?
• Argument gives an honest appearance
Fallacies
• Hasty/Faulty Generalization
• Inference drawn from insufficient evidence
• Because my Honda broke down, then all Hondas must be junk.
• Sweeping Generalization
• Claim that something applies to all situations without exceptions.
• All cameras are easy to use.
• All women are bad drivers.
• All English teachers are nitpicky.
Fallacies
• Post Hoc: Faulty Causality
• Assumes that because one action follows another, the first causes
the second
• The abnormally warm weather led to the increased number in
summer casualties
• Faulty Analogy
• Assuming that since two things are alike in one aspect, they must
be alike in others
• Employees are like nails. Just as nails must be hit in the head in order
to make them work, so must employees.
Fallacies
• Non-Sequitur
• Literally means “it does not follow.”
• A conclusion or statement that does not arise logically from the
premises of a given argument
• Because my sister is rich, she will make a good parent.
• Red Herring
• Introducing something irrelevant/tangential to change or shift the
topic
• Why should we worry about the amount of violence on television
when thousands of people are killed in automobile accidents every
year?
Fallacies
• Straw Man
• Strengthening your own view by distorting/oversimplifying the
opposing view
• Attacking an argument that isn’t really there.
• "Senator Jones says that we should not fund the attack submarine
program. I disagree entirely. I can't understand why he wants to
leave us defenseless like that.“
• Bandwagon
• Assumes that because something is popular, it is desirable, good,
or correct
• The President must be correct in his approach to foreign policy; after
all, the polls show that 60 percent of the people support him.
Relativist Fallacy
• More or less, this is the view that a claim could be true
for one person and false for another at the same time.
• Example:
• Jeff: “Scotty, why do you smoke? Don’t you know
smoking can cause lung cancer?
• Scotty (exhaling): “Maybe for other schmucks, but
not for me.”
• Or this.
Name that Logical Fallacy
• “Well, I vote Republican because my family has for as long back as I can
remember. They’re usually pretty right about most things.”
• Yeah, well, you’re stupid!”
• “How can you be against detention? You supervise it!”
• “Don’t listen to Bill say that we need to get off foreign oil. He drives a
diesel.”
• “You shouldn’t believe anything unless you can prove it.”
Name that Logical Fallacy
• “What do you mean school lunches should have only healthy foods?
Kids will never eat that! You want kids to starve?”
• “Well, if that’s what everyone wants…”
• “The only reason you want to raise taxes is because you are a
socialist. Why are you a socialist?”
• I believe murder is wrong, but I think it is OK if some cultures accept
it.
• Why should we listen to you? You’re a teacher’s pet.