Reasoning in Logos-Based Arguments and Logical Fallacies

1. Reasoning in Logos-Based Arguments and Logical Fallacies

2. Types of Reasoning • Arguments based on evidence and proof use logic. • Inductive reasoning: beginswith a series of specific facts or data (evidence) and moves to a general statement or conclusion based on the evidence. • Photo A taken indoors without a flash did not come out. • Photo B taken indoors without a flash did not come out. • Photo C taken indoors without a flash did not come out. • Conclusion: Photos taken indoors without a flash will not come out.

3. Inductive Reasoning • Evidence never absolutelyprovesthe conclusion is true. • Facts/evidence supportthe conclusion. • Weaker; only based on prior occurrences. 1. It has snowed in Massachusetts every December in recorded history. Therefore, it will snow in Massachusetts this coming December. 2. Having just arrived in Ohio, I saw a white squirrel. All Ohio squirrels are white.

4. Types of Reasoning • Deductive reasoning: beginswith a general or universal statement and moves to a specific, more limited statement. • Stronger; based on verifiable facts Example: Whichever basketball team scores the most points will win the game. Virginia scored more points than UNC. Therefore, Virginia won the game.

5. Types of Reasoning • Syllogism—a form of deductive reasoning made up of three parts: a majorpremise(a general or universal statement which is said to be true) , a minor premise and a conclusion. • Major Premise: Whichever basketball team scores the most points will win the game. • Minor Premise: Virginia scored more points than UNC. • Conclusion: Therefore, Virginia won the game.

6. Failures of Logic • Deductive arguments can fail if… • The major premise is not a universal statement or not universally accepted as true (trueof all, every, no, or none of the people, objects, or events that are the subject of the statement) • Major Premise: Whichever basketball team scores the most points will win the game. • Minor Premise: Virginia scored more points than UNC. • Conclusion: Therefore, Virginia won the game.

7. Failures of Logic • A major premise can never contain a limiter, such as some, most, or many. • Allan is allergic to some foods that contain wheat. • Spaghetti contains wheat • Allan is allergic to spaghetti.

8. Failures of Logic • Deductive arguments can fail if… • One of the premises is false If Burger King sells Big Macs, then McDonald’s will go out of business. Burger King does sell Big Macs. Therefore, McDonald’s will go out of business. • One or more of the premises is an unwarranted assumption; the conclusion does not properly follow from the premises Baptists are often politically conservative. Republicans are often politically conservative. Therefore, Baptists are often Republicans.

9. Logical Fallacies • Sometimes an argument based on logos seems logical when, according the the rules of logic, it isn’t. • Logical fallacies: flaws in the logic of an argument. • Rhetorical strategy used to persuade and convince an audience or to win an argument.

10. Circular Logic/Equivocation • Begins with an assumption you are trying to prove is true. • Uses the conclusion to support a premise that supports the conclusion; no useful information is shared • I’m right because I’m right. • There isn’t a problem with the rule because, if everyone obeyed it, it wouldn’t be a problem.

11. Ad hominem • From Latin: “against the person.” • Attacking the person making the argument, rather than the argument itself • Attack is irrelevant to the argument the person is making. • Example: • My opponent suggests that lowering taxes will be a good idea -- this is coming from a woman who eats a pint of Ben and Jerry’s each night! • Ms. Bauer is an incompetent math teacher. She always wears blue jeans.

12. Appeal to tradition/common practice • The fact that most people do something is used as evidence to support the action or practice. • The mere fact that most people do something does not make it correct, moral, justified, or reasonable. • Example: • Hey officer, why did you stop me? Everybody else on the freeway was speeding. • Marriage has traditionally been between a man and a woman; therefore, gay marriage should not be allowed.

13. Appeal to ignorance • This fallacy occurs when a lack of evidence is taken to be evidence. • Example: • Bill: "I think that some people have psychic powers." • Jill: "What is your proof?" • Bill: "No one has been able to prove that people do not have psychic powers." • Suds ‘n Spuds is a great restaurant; no one has reported anyone dying of food poisoning yet.

14. Ignoring the question/Red Herring • An argument used to evade or redirect attention from a topic discussed to one the person doing the redirecting can better respond. • Example: • I should not pay a fine for reckless driving. There are actual dangerous criminals on the street, and the police should be chasing them instead of harassing a decent tax-paying citizen like me.

15. Appeal to popularity/Bandwagon • The Bandwagon is a fallacy in which a threat of rejection by one's peers (or peer pressure) is substituted for evidence in an argument. • Example: • You definitely need to buy those boots. Everyone is wearing them. • Dude, you don’t really listen to Britney Spears, do you?

16. Slippery Slope • An assertion that some event must inevitably follow from another. • No reason is given as to why the probable intervening steps or gradations would be bypassed. • Example: • We've got to stop them from banning pornography. Once they start banning one form of literature, they will never stop. Next thing you know, they will be burning all the books!

17. Either/Or Fallacy/ False Dilemma • An argument in which only two alternatives are considered, when in fact there are other options. • Example: • Look, you are going to have to make up your mind. Either you decide that you can afford this stereo, or you decide you are going to do without music for a while.

18. Straw Man • Substituting a person’s actual position or argument with a distorted, exaggerated, or misrepresented version of the position of the argument. • Example: • Jill: "We should clean out the closets. They are getting a bit messy." • Bill: "Why, we just went through those closets last year. Do we have to clean them out everyday?" • Jill: "I never said anything about cleaning them out every day. You just want to keep all your junk forever, which is just ridiculous."

19. Hasty Generalization • This fallacy is committed when a person draws a conclusion about a population based on a sample that is not large enough. This is an extremely weak form of inductive reasoning. • Example: • My father smoked four packs of cigarettes a day since age fourteen and lived until age sixty-nine.  Therefore, smoking really can’t be that bad for you.

20. Post Hoc Ergo Propter Hoc • "After this, therefore because of this." • This fallacy is committed when it is concluded that one event causes another simply because the proposed cause occurred before the proposed effect. • Example: • Joan is scratched by a cat while visiting her friend. Two days later she comes down with a fever. Joan concludes that the cat's scratch must be the cause of her illness.