Logical Fallacies

Poisoning the well

Fallacy occurs when a speaker or writer attempts to dismiss what someone is going to say by talking about the person's character or circumstances or consistency. Presenting negative information about a person before he/she speaks so as to discredit the person's argument. Example: Frank is pompous, arrogant, and thinks he knows everything. So, let's hear what Frank has to say about the subject. Example: Don't listen to him because he is a loser.

Hasty Generalization

Generalizing from too few cases. Taking specific statements and turning into big generalization. Writing tires to support a general statement or rule by citing too few supporting cases. (Lonely fact, anecdote, small sample, exceptional case, generalizing from too few cases).

Argument by Anecdote

Hasty generalization; a story. When a speaker or writer tries to support a general claim by offering a story.

Weak (Faulty/False) Analogies

Is a weak argument based on debatable or unimportant similarities between two or more things. Lead to faulty conclusions. Be sure the ideas you're comparing are really related. Example: Forcing students to attend cultural events is like herding cattle to slaughter. The students stampede in to the event where they are systematically "put to sleep" by the program.

Guilt by Association

Occurs when a speaker or writer tries to persuade us to dismiss a belief by telling us that someone we don't like has that belief. Rejecting an argument or claim because the person proposing it likes someone that is disliked by another. Example: Hitler liked dogs. Therefore dogs are bad. Example: Your friend is a thief. Therefore, I cannot trust you.

Irrelevant Conclusion

Relevance fallacies that do not fit comfortably in one of the listed categories may be said to commit this fallacy.

False Dilemma

This fallacy happens when someone tries to establish a conclusion by offering it as the only alternative to something we will find unacceptable, unattainable, or implausible. Assuming hat only two alternatives exist. Either A or B. If not A therefore B. Two choices are given when in actuality there could be more choices possible. Example: You either did knock the glass over or you did not. Which is it? Example: Do you still beat your wife?

Post Hoc, Ergo Propter Hoc

"After this, therefore because of it." A speaker commits this fallacy when he or she assumes that the fact that one event came after another establishes that it was caused by the other. A fallacy with the following form. 1. A occurs before B. 2. Therefore, A is the cause of B. Example: Eating five candy bars and drinking two sodas before a test helps me get better grades. I did that and got an A on my last test in history. Example: The picture on Jim's old TV set goes out of focus. Jim goes over and strikes the TV soundly on the side and the picture goes back into focus. Jim tells his friend that hitting the TV fixed it.

Cum Hoc, Ergo Propter Hoc

"With this, therefore b/c of it." A speaker or writer commits this fallacy when he or she assumes that the fact that two events happen at about the same time establishes that one caused the other.

Equivocation

A fallacy occurs when a speaker or writer attempts to demonstrate or support a point by playing on the ambiguity of expression. The same term is used in an argument in different places but the word has different meanings. Example: A bird in the hand is worth two in the bush. Therefore, a bird is worth more than President Bush. Example: Evolution states that one species can change into another. We see that cars have evolved into different styles. Therefore, since evolution is a fact in cars, it is true in species.

Two Wrongs Make a Right

A fallacy occurs when a speaker or writer thinks that wrongfulness of a deed is erased by it being a response to another wrongful deed.

Appeal to Peer Pressure

A fallacy occurs when a speaker or writer tires to persuade us to do or accept something by playing on our fear of becoming an outcast if we don't. The hearer is urged to accept a position because a majority of people hold to it. Example: The majority of people like soda. Therefore, soda is good. Example: Everyone else is doing it. Why shouldn't you?

Confusing Explanations with Excuses

An attempt to excuse or justify a thing or event requires an argument that the conclusion of which is that the thing or event is justifiable or excusable. But an attempt to explain the thing or event with excuses requires a story--an account of a causal chain--showing how the thing or event may have come to be.

Division

Assuming that what is true of the group or whole of things taken collectively must also be true for the parts of those same things taken individually. What is true for the whole is true for the parts. Example: That car is blue. Therefore, its engine is blue. Example: Your family is weird. That means that you are weird too.

Ad hominem

Attacking the individual instead of the argument. The most common fallacy. You commit this fallacy if you think you dismiss someone's position (idea, proposal, claim, argument, etc.) by dismissing him or her. Example: You are so stupid you argument couldn't possibly be true. Example: I figured that you couldn't possibly get it right, so I ignored your comment.

Genetic Fallacy

Fallacy is committed when he or she argues that the origin of a contention (heated disagreement) in and of itself automatically renders it false. The attempt to endorse or disqualify a claim because of the origin or irrelevant history of the claim Example: The Nazi regime developed the Volkswagen Beetle. Therefore, you should not buy a VW Beetle because of who started it. Example: Frank's just got out of jail last year and since it was his idea to start the hardware store, I can't trust him.

Begging the Question

Fallacy is committed when the speaker or writer is guilty of begging the question logically when he or she tries to "support" a contention by offering as "evidence" what amounts to a repackaging of the very contention in question. (Circular reasoning; starting too close to the conclusion). Assuming the thing to be true that you are trying to prove. It is circular. Example: Women shouldn't be allowed in combat, b/c it's prohibited by the Defense Department. Example: God exists because the Bible says so. The Bible is inspired. Therefore, we know that God exists. Example: I am a good worker because Frank says so. How can we trust Frank? Simple. I will vouch for him.

Composition

Fallacy occurs when a feature of the parts of something is erroneously attributed to the whole. Example: The building is built from rectangular bricks; therefore, it must be rectangular.

Argument from ignorance

The fallacy of assuming that something is true/false because it has not been proven false/true. Example: "The student has failed to prove that he didn't cheat on the test, therefore he must have cheated on the test." Example: 'U.F.Os must exist, because no one can prove that they don't."

Red Herring

The introduction of a topic not related to the subject at hand. Example: I know your car isn't working right. But, if you had gone to the store one day earlier, you'd not be having problems. Example: I know I forgot to deposit the check into the bank yesterday. But, nothing I do pleases you.

Relevance Fallacy (red herrings)

The premise is not relevant to the issue in question. All called red herrings; distracting irrelevancy.

Cause and Effect

The timing of two variables relation with one another in of itself that is sufficient to establish that one thing is the cause of another. Assuming that the effect is related to a cause because the events occur together. Example: When the rooster crows, the sun rises. Therefore, the rooster causes the sun to rise. Example: When the fuel light goes on in my car, I soon run out of gas. Therefore, the fuel light causes my car to run out of gas.

Analogues

Things have similar attributes. Attribute of interest: the attribute ascribed to a thing or things in the conclusion of an inductive argument. Conclusion analogue: the analogue refereed to in the collusion for an argument from analogy. Premise analogue: An argument from analogy is an argument that has an attribute b/c a similar thing has that attribute. The similar thing is the premise analogue. Argument of Analogy: An argument that something has an attribute b/c a similar thing has that attribute. Example: Darby is an excellent dog sitter. Therefore she would be an excellent babysitter. Premise analogue is the dog sitter and conclusion analogy is babysitter. Attribute of interest is "excellent."

Slippery Slope

This fallacy is an argument that rests on an unsupported warning that is controversial and tendentious, the effect that something will progress by degrees to an undesirable outcome. When predicting that if one thing happens or is permitted to happen, there is no reason to think that x-y-z (bad). If we do a, then b follows, then c... and c is very bad. Need a principle stopping point to prove fallacy wrong). Suggests that one step will inevitably lead to more, eventually negative steps. Example: We have to stop the tuition increase! The next thing you know, they'll be charging $40,000 a semester! Example: You can never give anyone a break. If you do, they'll walk all over you.

Perfectionist Fallacy

This fallacy is committed when a speaker or writer ignores options between "perfection" and "nothing." Example: A single English course won't make anyone a great writer, so I don't see why we have to take it. (The fact that it could make you better though is the other alternative).

Line-Drawing Fallacy

This fallacy occurs when a speaker or writer assumes that either a crystal-clear line can be drawn b/t two things, or there is no difference b/t them. Example: Poverty isn't a problem in this country; after all, when is a person really poor? You can't say exactly.

Straw Man Argument

This fallacy occurs when a speaker or writer attempts to dismiss contention by distorting or misrepresenting it. Producing an argument to attack that is a weaker representation of the truth. Example: The government doesn't take care of the poor because it doesn't have a tax specifically to support the poor. Example: We know that evolution is false because we did not evolve from monkeys. Example: This weekend we should clean out a corner of the garage. Are you kidding me? I'm not going to spend the whole weekend cleaning out the entire garage.

Scare Tactics

This fallacy occurs when a speaker or writer tires to scare us into accepting an irrelevant conclusion.

Appeal to Emotion

When a speaker or writer "supports" a contention by playing on our emotions rather than producing a real argument. (Appeal to pity, outrage, envy, etc.)

Accident

When a speaker or writer assumes that a general statement automatically applies to a specific case that is or could well be exceptional. Starts with general statement and goes to specific conclusion. Example: Walmart has the lowest prices. Therefore these jeans will be cheaper at Walmart.

Bandwagon Fallacy

When a speaker or writer uses "everyone thinks" as a psychological ploy, he or she commits this fallacy. A threat of rejection by one's peers (or peer pressure) is substituted for evidence in an "argument." Example: Fifty million Elvis fans can't be wrong!

Misplacing Burden of Proof

When people try to support or prove their position by misplacing the burden of proof.

Wishful Thinking

When someone forgets that wanting something to be true is irrelevant to whether it is true.