1. The Seven Deadly Logical Sins Ways to use logic as a shield
Spot Fallacies
The Seven Deadly Logical Sins
Ways to use logic as a shield

2. 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.

3. Spot Fallacies
Elephants are animals. You are an animal. That makes you an elephant.

4. 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.”

5. Spot Fallacies
Tautology—repeating the same thing as if I am proving something. “All logical fallacies come down to bad logic.”

6. Spot Fallacies Does a fallacy lie hidden in an argument?
Does the proof hold up?
Am I given the right number of choices?
Does the proof lead to the conclusion?
Who cares?

7. 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.”

8. 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).

9. Spot the Fallacies
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

10. Spot the Fallacies
The Fallacy Fallacy-- WMrlIQ&index=2&list=PLtHP6qx8VF7dPql3ll1To4i6vEIPt0kV5

11. Spot Fallacies
First Deadly Sin: The False Comparison “Made with all natural ingredients.” …all natural… or …all-natural… The ambiguity fallacy.

12. Spot Fallacies
Purple is not a fruit!

13. Spot Fallacies
The all natural fallacy assumes that members of the same family assume the same traits.

14. Spot Fallacies
The appeal to popularity legitimizes your choice by claiming that others have chosen it.

15. Spot Fallacies
Reductio ad absurdum—reducing an argument to absurdity. (The premise is unbelievable.)

16. 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.”

17. Spot Fallacies
The false analogy… Candidate: I’m a successful business man. Elect me and I will run a successful city.

18. Spot Fallacies
Anthropomorphism—screaming trees?

19. Spot Fallacies
Unit fallacy--mistaking one kind of unit for another. (Keep track of the difference between a piece of the pie and the whole pie.)

20. Spot Fallacies
Read the discussion about the cost of detergent ( ). (unit fallacy)

21. Spot Fallacies
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.)

22. Spot Fallacies
Proper Rhetorical Reply: Good! That’ll keep a couple more potential criminals off the streets.

23. Spot Fallacies
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?

24. 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.

25. Spot Fallacies
Proof: The lab tests are all negative. So… Conclusion: Nothing is wrong with you.

26. Spot Fallacies
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.

27. Spot Fallacies
It is also called “begging the question”. “You can trust our candidate because he is an honest man.”

28. Spot Fallacies
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.

29. Spot Fallacies
The false dilemma—you are given two choices when you actually have many choices. <The cat fancier discussion, Pg. 147 – 148>

30. Spot Fallacies
The complex cause fallacy—Only one cause gets the blame (or credit) for something that has many causes. <The faulty motorcycle helmet>

31. Spot Fallacies
The Sixth Deadly Sin: The Red Herring The red herring (the Chewbacca defense)—Switches issues in mid- argument to throw the audience off the sent.

32. Spot Fallacies
The straw man tactic—a version of the red herring fallacy; it switches topics to one that is easier to fight.

33. Spot Fallacies
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.

34. Spot Fallacies
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

35. Spot Fallacies
The post hoc ergo propter hoc fallacy (the chanticleer fallacy)—after this, therefore because of this.

36. Spot Fallacies
“Our newsletter is a big success. After we started publishing it, alumni giving went up.”