Common Logical Fallacies

1. Common Logical Fallacies #1 When a Reason/Proof Isn’t

2. Using Analogies • Definition: explaining the unfamiliar by comparing it to the familiar • Can help explain abstract concepts, clarify important ideas • Limited: NOT a proof • Ignores dissimilarities, differences of class

3. Example: Overcrowding in cities is like putting many rats in a small cage. Like rats, people will turn on each other, fighting and killing until balance is restored. For this reason, we need to put more money into low cost housing.

4. Non Sequitur (It Does Not Follow) • The conclusion doesn’t follow or make sense with the arguments or lead up reasons. • Example: Disarmament weakened the US after WWI. Disarmament weakened the US after Viet Nam. Therefore, gun control will weaken the US. • Example: Don’t eat catfish. They’re sneaky and mean.

5. Begging the Question (Circular Thinking) • Assumes as a reason/proof something that is really part of your thesis, something you should be trying to prove. • Example: Unfair and shortsighted legislation limiting free trade is a threat to the economy. Because it limits people’s right to trade the way they want, it is unjust and hurts trade. • Example: I don’t like those shoes. They just don’t do anything for me. I don’t have a happy feeling when I look at them.

6. Either/Or (False Dilemma/ Black and White Thinking) • Suggests that only two (extreme) alternatives exist, when there may be many more. • Example: We must choose between life and death, between intervention and genocide in Bosnia. • Example: If you don’t let me TA for two periods, I’ll have to drop out of school.

7. Arguing from Ignorance • Argues that if it hasn’t been proved true, it must be false; or if it hasn’t been proved false, it must be true. • Example: Marijuana use doesn’t lead to hard drugs. Show me one study that proves that it does! • Example: Chocolate helps stomach cramps. It never has been proved that it doesn’t.

8. After This/Because of This(Post Hoc Ergo Propter Hoc) • Assumes that just because one event closely followed another in time, the first one caused the second. • Example: Maryann didn’t have many dates. She used Smorc hairspray. Murgatroyd asked her out. Obviously, Smorc hairspray is a miraculous product.

9. Hasty/Sweeping GeneralizationsDicto Simplicite • Jumping to a conclusion based on too little evidence • Condemning or praising all in a group for the qualities of a few of the group • Example: • Our son benefited from preschool; the government should fund preschools for all. • Don’t go out with that snowboarder: they’re all into partying, drinking and drugs.

10. Stereotypinga type of sweeping generalization • Judging an individual or assigning an individual characteristics based on a preconceived opinion of the group to which the individual belongs • Example: She wouldn’t like that AP philosophy class. She’s a blonde cheerleader.

11. Fallacy of Division • Assuming that if the whole unit has a quality, each of its parts must also have the quality • Example: There are only 80 calories in this chocolate milk. Cocoa must not contain as much fat as I thought.

12. Fallacy of Composition • Assuming that since every part has a particular characteristic, the whole must share the characteristic. • Example: • I love pizza, and I love milkshakes. Pizza milkshakes must really taste good! • That motor comes from Korea, and it is good quality. So does the chassis, and it is also good quality. That Kia must be a really quality car.

13. Label which kind of generalization applies: • She has had training as a dietitian and as a nurse. She would make a good hospital cook. • You’re going to the dance with Uriah? I thought he was a computer nerd. • I’d never go to Provo Towne Center to buy my dress. Everything there is expensive. I priced a formal there once, so I know. • Each of those five boys is kind of shy. They couldn’t possibly compete as a team at that math competition. They wouldn’t be aggressive to stand up against other teams.