Transcript Spot Fallacies

Spot Fallacies
The Seven Deadly Logical Sins
Ways to use logic as a shield
Spot Fallacies
Homer: Lisa, would you like a doughnut?
Lisa: No, thanks. Do you have any fruit?
Homer: This has purple in it. Purple is a fruit.
Spot Fallacies
Elephants are animals.
You are an animal.
That makes you an elephant.
Spot Fallacies
“All logical fallacies come down to…bad logic. In the logic of deliberative
argument, you have the proof and a choice. // It starts with what the
audience knows or believes—the commonplace—and applies it to a
particular situation to prove your conclusion. In deduction, the
commonplace serves as your proof. The proof in induction is a set of
examples.”
Spot Fallacies
Tautology—repeating the same thing as if I am proving something.
“All logical fallacies come down to bad logic.”
Spot Fallacies
Does a fallacy lie hidden in an argument?
1)
2)
3)
4)
Does the proof hold up?
Am I given the right number of choices?
Does the proof lead to the conclusion?
Who cares?
Spot Fallacies
“In rhetoric, on the other hand, there are really no rules. You can
commit fallacies to your heart’s content, so long as you get away with
them. Your audience bears the responsibility to spot them; but if it
dies, there goes your ethos.”
Spot Fallacies
Bad Proofs—include three sins: false comparison (lumping examples of
the wrong category), bad example, and ignorance as proof (asserting
that the lack of examples proves something.)
Wrong number of choices—covers one essential sin, the false choice:
offering just two choices when more are available, or merging two or
three issues into one.
Disconnect between proof and conclusion—results in the tautology (in
which the proof and the conclusion are identical), the red herring (a
sneaky distraction), or the wrong ending (in which the proof fails to
lead to the conclusion).
Spot the Fallacies
https://www.youtube.com/watch?v=8qb-h0sXkH4
Strawman—1:50
Ad Hominem—3:45
Ad Homiem Tu quoque—4:39
The Black & White Fallacy—5:50
The Authority Fallacy—7:40
The No-True-Scotsman Fallacy—9:30
Spot the Fallacies
The Fallacy Fallacy--https://www.youtube.com/watch?v=oGBOWMrlIQ&index=2&list=PLtHP6qx8VF7dPql3ll1To4i6vEIPt0kV5
Spot Fallacies
First Deadly Sin: The False Comparison
“Made with all natural ingredients.”
…all natural… or …all-natural…
The ambiguity fallacy.
Spot Fallacies
Purple is not a fruit!
https://www.youtube.com/watch?v=0ak7GZxpF2U
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The all natural fallacy assumes that members of the same family
assume the same traits.
Spot Fallacies
The appeal to popularity legitimizes your choice by claiming that
others have chosen it.
Spot Fallacies
Reductio ad absurdum—reducing an argument to absurdity.
(The premise is unbelievable.)
Spot Fallacies
The fallacy of antecedent…
Driver: I don’t have to slow down. I haven’t had an accident yet.
(It never happened before, so it never will. / It’s happened before, so it
will happen again.)
“My dog doesn’t bite.”
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The false analogy…
Candidate: I’m a successful business man. Elect me and I will run a
successful city.
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Anthropomorphism—screaming trees?
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Unit fallacy--mistaking one kind of unit for another.
(Keep track of the difference between a piece of the pie and the whole
pie.)
Spot Fallacies
Read the discussion about the cost of detergent (143-144). (unit
fallacy)
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Second Deadly Sin: The Bad Example
Misinterpreting the evidence—
Parent: Seeing all those crimes on TV makes me want to lock up my
kids and never let them out.
(Evidence doesn’t support the conclusion.)
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Proper Rhetorical Reply: Good! That’ll keep a couple more potential
criminals off the streets.
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The hasty generalization offers too few examples to prove the point.
Coworker: That intern from Yale was great. Let’s get another Yalie.
Proper Rhetorical Reply: Didn’t that jerk in Legal go to Yale?
Spot Fallacies
Third Deadly Sin: Ignorance as Proof
The fallacy of ignorance—If we can’t prove it, then it must not exist.
Or, if we can’t disprove it, then it must exist.
Doctor: There’s nothing wrong with you. The lab tests came back
negative.
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Proof: The lab tests are all negative. So…
Conclusion: Nothing is wrong with you.
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Fourth Deadly Sin: The Tautology
The tautology basically just repeats the premise.
Fan: The Cowboys are favored to win since they’re the better team.
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It is also called “begging the question”.
“You can trust our candidate because he is an honest man.”
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The Fifth Deadly Sin: The False Choice
Many Questions: Two or more issues get squashed into one, so that a
conclusion proves another conclusion.
The “when did you stop beating your wife” ploy.
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The false dilemma—you are given two choices when you actually have
many choices.
<The cat fancier discussion, Pg. 147 – 148>
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The complex cause fallacy—Only one cause gets the blame (or credit)
for something that has many causes.
<The faulty motorcycle helmet>
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The Sixth Deadly Sin: The Red Herring
The red herring (the Chewbacca defense)—Switches issues in midargument to throw the audience off the sent.
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The straw man tactic—a version of the red herring fallacy; it switches
topics to one that is easier to fight.
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The Seventh Deadly Sin: The Wrong Ending
The slippery slope—if we allow this reasonable thing, it will inevitably
lead to an extreme version of it.
Parent: If I let you skip dinner, then I’ll have to let the other kids skip
dinner.
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Mixing up cause and effect—
“Budget cuts are ruining our children!”
The best argument against the slippery slope is concession. The
slippery slope has a built-in reduction ad absurdum
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The post hoc ergo propter hoc fallacy (the chanticleer fallacy)—after
this, therefore because of this.
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“Our newsletter is a big success. After we started publishing it, alumni
giving went up.”