Logical Fallacies

Fallacy An improper argumentation in reasoning that leads to a misconception or presumption. Often appeal to emotion or take advantage of social relationships Goal is to obscure logical argument

Appeal to Authority Cites an authority who is not qualified to have an expert opinion Cites an expert when other experts agree on the issue Cites an expert by hearsay only Examples: “Firemen support Jones as the best choice for our town’s future.” (in reality, firefighters would really only be experts on fire safety) “Dr. Smith refutes scientists’ evidence that global warming exists.” (the vast majority of scientists agree that it does, but this expert does not)

Appeal to Force Predicts dangers outcomes if you follow a course other than the speaker’s Examples: “This kind of economic policy will lose you your job and ruin your children’s futures.” (Is there evidence that it is so? Could there be evidence to show it might even build prosperity and create jobs?) “Legalizing same-sex marriage would lead to the destruction of society and to families as we know them.” (What evidence is there of this happening? Is there any at all?)

Appeal to Popularity Also known as “bandwagon” Holds an opinion to be valuable because large numbers of people support it Examples: “Polls show that Americans prefer their current health care system.” (Are there options? Could the majority be missing something?) “4 out of 5 dentists recommend Trident gum.” (Would they also recommend other types of gum? Is this the only acceptable brand?)

Attacking the Person Also known as “Ad Hominem” Attacks the person making the argument instead of the argument Attacks the person making the argument because of those with whom he/she associates Insinuates the person making the argument would stand to gain by it Example: “Certainly he’s in favor of a tax break for millionaires – he’s rich!” (Could other people be benefitting, too?)

False Dilemma Offers a limited number of options – usually two – when there are actually more choices Examples: “Either we continue the failed war against drugs and lose another generation or make marijuana legal.” (are there other ways to deal with the drug issue?) “Either you stand behind Mitt Romney, or President Obama will win again in 2012.” (What about the other Republican candidates?)

Hasty Generalization Uses a sample too small to support the conclusion Examples: “We’ve seen here in Smallville’s widget factory that free trade doesn’t help the American worker.” (How about the millions of workers elsewhere?) “Polls in Iowa show that Rick Santorum is the clear front-runner for the GOP.” (Is Iowa a big enough and accurate enough representation of the American people?)

Slippery Slope Threatens a series of increasingly dire consequences from taking a simpler course of action Examples: “First it’s gun show laws, and then they’ll come to confiscate all guns, and then we’ll lose democracy altogether.” (Do gun laws imply eventual confiscation?) “Once we open up marriage to be redefined to include gay people, it will lead to redefining it to allow polygamy, incest, and marrying pets.” (Are these things really the same?)

Appeal to Emotion This sort of “reasoning” involves the substitution of various means of producing strong emotions in place of evidence for a claim Examples: “You must believe that God exists. After all, if you do not accept that God exists, then you face going to hell.” (how does this argument appeal to emotion rather than reason?) “If you do not vote for Candidate X, you are dooming your country to four years of tyranny and horrendous consequences for the American people.” (How? Where is the evidence?)

Appeal to Tradition This occurs when it is assumed that something is better or correct simply because it is older, traditional, or has “always been done.” Examples: “Sure I believe in God. People have believed in God for thousands of years, so it seems clear that God must exist.” (Evidence? Reason?) “Of course marriage should remain between a man and a woman. It’s been like that for thousands of generations, so it shouldn’t change now.”

Begging the Question A fallacy in which the conclusion occurs as one of the premises Example: Bill: God must exist. Jill: How do you know? Bill: Because the Bible says so. Jill: Why should I believe the bible? Bill: Because the Bible was written by God. (belief in God then is a foregone conclusion)

Genetic Fallacy Occurs when a perceived defect in the origin of a claim or thing is taken to be evidence that discredits the claim or thing itself. Examples: “The current Chancellor of Germany was in the Hitler Youth at age 3. With that sort of background, his so-called ‘reform’ plan must be a fascist program.” (Because of his colored past, each decision he makes is marred by it.) “She used to be an alcoholic, so I wouldn’t trust anything she says.” (her past problems make discredit everything she says now?)

Red Herring Committed when an irrelevant topic is presented in order to divert attention from the original issue Topic A is under discussion. Topic B is brought up under the guise of being relevant to Topic A. Topic A is no longer being discussed, as all attention has turned to Topic B. Example: “We must go to war and take out that country’s dictator because of all of the terrible things he does to his people. And he has Weapons of Mass Destruction! WMD are a threat to the entire world and must be eliminated. We must confiscate the dictator’s WMD!”

Straw Man Committed when a person simply ignores a person’s actual position and substitutes a distorted, exaggerated or misrepresented version of that position. Examples: “I don’t believe in evolution because I don’t believe we evolved from monkeys.” “Candidate B does not support forcing insurance companies to cover birth control for women. Candidate B is a misogynist who does not understand or respect women’s health issues.”

Post hoc, Propter hoc After this, therefore because of this Committed when it is concluded that one event causes another simply because the proposed cause occurred before the proposed effect. Examples: “Jeff walked under a ladder, and the next day, he failed his math test. He now knows that walking under a ladder causes bad luck.”