Common fallacies to avoid Statements that weaken arguments...

Weak Arguments illogical statementsfallaciesWeak arguments rely on illogical statements called fallacies. The following slides contain examples of logical fallacies...The following slides contain examples of logical fallacies...

Non-sequitur Non-sequitur- ("it does not follow") “Non-SECK-quit-er” An inference or conclusion that does not follow from established premises or evidence.Examples: The President graduated from Harvard. He can't make mistakes. She rides a motorcycle, so she must be a chef. The judge didn’t smile at me. She must hate me.

Circular Reasoning repeats a premise rather than giving a valid reason.Examples: because she supervises the company's personnel office effectively.Martha is a good supervisor because she supervises the company's personnel office effectively. Only a fatalist would bungee jump, and the fact that bungee jumpers are fatalists is proof of this.

Ad Hominem (to the man) attacks the person rather than the issue.attacks the person rather than the issue. Examples: Sam is divorced, so how can he make sound financial decisions for the city? Mr. Spock is not an effective second-in- command because he has ugly pointed ears. Dr. Kirkegard’s books about plant genetics are worthless because he is a convicted forger and embezzler.

Over-generalization draws a conclusion about an entire group based on insufficient evidence.draws a conclusion about an entire group based on insufficient evidence.Examples: I know five Italians who like pizza, so all Italians must like pizza. Since Warren Buffet and Bill Gates made large gifts to charitable causes, all wealthy men must be charitable.

Post hoc, Ergo Propter Hoc (“after this; therefore because of this”) attributes a cause/effect relationship simply because something occurs after something else. (“black cat” reasoning) Examples: A black cat crossed my path before I took the math test; I ended up failing the test because of that cat! I did not send a thank you note to the recruiter. Jenny was offered the job. Jenny got the job because I forgot to send a thank you note.

False Dichotomy there are only two possibilities Either/Or” fallacy. Most situations provide more than two possible outcomes....based on the false assumption that there are only two possibilities. Sometimes called the “Either/Or” fallacy. Most situations provide more than two possible outcomes. Examples: Either you are with America's fight against terrorism or you are America's enemy. “She likes. She likes me not. She likes me. She likes me not.”“She likes. She likes me not. She likes me. She likes me not.” Either we change locations or close this business down all together.Either we change locations or close this business down all together. If we don’t agree on this issue completely now, or we will eventually get a divorce!If we don’t agree on this issue completely now, or we will eventually get a divorce!

Red Herring The Red Herring occurs when one draws attention away from the main issue by focusing on a side issue or on something irrelevant....named after a strong-smelling fish, the scent of which throws hounds off the scent of a trail. The Red Herring occurs when one draws attention away from the main issue by focusing on a side issue or on something irrelevant. Examples: "So you think that doctor-assisted suicide is morally acceptable? You probably also think that an unborn human being is just a 'choice'.”"So you think that doctor-assisted suicide is morally acceptable? You probably also think that an unborn human being is just a 'choice'.” "I work 60 hours a week to support my family, and I pay my taxes; you shouldn't arrest me just because I punched him in the face.”"I work 60 hours a week to support my family, and I pay my taxes; you shouldn't arrest me just because I punched him in the face.” You’re not being fair by denying me the opportunity to make up the quiz; after all, I’m paying for my own education, I work two jobs and have to raise my six children on my own!You’re not being fair by denying me the opportunity to make up the quiz; after all, I’m paying for my own education, I work two jobs and have to raise my six children on my own!

Appeal to the Crowd- relying on the emotional passion of the crowd in making an argument; playing on a group's fears or prejudices.Examples: We will all go broke if we don't put a stop to welfare fraud. All I can say is that if enjoying junk food is unhealthy, then the majority of us are unhealthy! Just ask anyone in Professor Campbell’s class if the latest test was extremely unfair. Just ask anyone in Professor Campbell’s class if the latest test was extremely unfair.

Appeal To Tradition: do things as they have been done in the past.... We should continue to do things as they have been done in the past. We shouldn't challenge time-honored customs or traditions. (“don't rock the boat”) Of course you have to play “Here Comes the Bride" at your wedding, because that's always been the song that is played. We always have liver on Thanksgiving even though we dislike it because it’s been a family tradition for generations.We always have liver on Thanksgiving even though we dislike it because it’s been a family tradition for generations.

Burden of Proof The burden of proof is always on the person making an assertion or proposition. Shifting the burden of proof, is a fallacy. Essentially the arguer claims that he should win by default if his opponent can't make a strong enough case. “Vampires really exist” “How do you know?” “Well, can you prove that they don’t exist?” “I guess not.” “Then Vampires must exist.”

Many more logical fallacies exist... Be on the lookout for them End of Presentation.