Common logical fallacies to avoid :Common logical fallacies to avoid Statements that weaken arguments...


Argument :Argument An argument can be supported by... logic (logos), an appeal to reasoning such as deductive and inductive; ethics (ethos), an appeal to one's sense of right and wrong or good sense, or to emotions (pathos), an appeal to one’s patriotism, fears, or sympathies.


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


Non-sequitur- ("it does not follow") :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 lesbian.


Begging the Question :Begging the Question Basing an argument on an assumption that has not been proven or that is impossible to prove. Examples: Synthetic vitamins are dangerous to one's health, so all of them should be removed from the store shelves. Teaching evolution is contrary to what God wants; therefore, the theory of evolution comes directly from Satan. People who watch little or no TV are generally more active than people who watch a lot of TV because the major networks send subliminal messages to make people passive, sleepy, and wanting more TV.


Circular Reasoning :Circular Reasoning repeats a premise rather than giving a valid reason. Examples: 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.


Straw-man Argument :Straw-man Argument attributes untrue characteristics to an argument and then attacks the argument based on those characteristics. Examples: "Evolution is false! How could a mouse evolve into an elephant!?" You’re a bad driver, so that’s why you won't support a bill to raise the driving age to twenty-one.


Ad Hominem (to the man) :Ad Hominem (to the man) 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 :Over-generalization 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 Procter Hoc :Post hoc, Ergo Procter 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! Our weather patterns have changed since we began launching the space shuttle into space.


False Dichotomy :False Dichotomy ...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. If you don’t take this trip now, you will either live with lifelong regret or you will take a better trip later in your life.


Red Herring :Red Herring ...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'.” "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!


Appeal to the Crowd- :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.


Appeal To Tradition: :Appeal To Tradition: ...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.


Many more logical fallacies exist... :Many more logical fallacies exist... Be on the lookout for them in your CARP reading and research! (See Patterns pgs. 542-543) End of Presentation.