Logical Fallacies
poisoning the well:
pre-emptive ad hominem attack against an opponent.
Adverse information (be it true or false) about person A is presented.
Therefore, the claim(s) of person A will be false.
Tim: Boss, you heard my side of the story why I think Bill should be fired and not me. Now, I am sure Bill is going to come to you with some pathetic attempt to weasel out of this lie that he has created.
I hope I presented my argument clearly. Now, my opponent will attempt to refute my argument by his own fallacious, incoherent, illogical version of history.
wishful thinking:
My husband has been missing for over ten years, but I know he's still alive. He just couldn't be dead.
There is a perfect marriage partner out there for everyone in this world. That is what everyone wants--a perfect marriage. If you look hard enough for it and then work hard enough at it, you'll have a perfect marriage.
There must be life after death because almost all people desire it. It is part of the very nature of human beings to desire it. If there were no life after death, then why would humans desire it? Like the desires for food, water, and sex, all of which are satiable, the desire for life after death is universal.
I don't think that there will be a nuclear war. If I believed that, I wouldn't be able to get up in the morning. I mean, how depressing.
I believe that when we die, we are all given new, young, perfect bodies, and we spend eternity with those whom we love. I can’t imagine the point of life if it all just ends when we die!
I acknowledge that I have no argument for the existence of God. However, I have a great desire for God to exist and for there to be an afterlife. Therefore, I accept that God exists.
two wrongs make a right: assuming that if one wrong is committed, another wrong will cancel it out. Often the other wrong action is of the same type a sub fallacy of tu quoque, and similar to red herring.
Logical Form:
1. Person A did X to person B.
2. Therefore, Person A is justified to do X to person B.
1. Person A believes that person B would do X to person A.
2. Therefore, Person A is justified to do X to person B.
This sort of "reasoning" is fallacious because an action that is wrong is wrong even if another person would also do it.
Jill is horrified by the way the state uses capital punishment. Bill says that capital punishment is fine, since those the state kill don't have any qualms about killing others.
Speaker A: You shouldn't embezzle from your employer. It's against the law.
Speaker B: My employer cheats on their taxes. That's against the law, too!
Weather Underground terrorist Bill Ayers, from his memoir Fugitive Days, defending a bombing attack by the Weathermen on the Pentagon: "The operation cost just under $500, and no one was killed, or even hurt. In that same time the Pentagon spent tens of millions of dollars and dropped tens of thousands of pounds of explosives on Viet Nam, killing or wounding thousands of human beings, causing hundreds of millions of dollars of damage. Because nothing justified their actions in our calculus, nothing could contradict the merit of ours."
It looks like the waiter forgot to charge us for the expensive bottle of champagne. Let’s just leave--after all, if he overcharged us, and I doubt he would chase us down to give us our money back that we overpaid.
red herring: a fallacy in which an irrelevant topic is presented in order to divert attention from the original issue. The basic idea is to "win" an argument by leading attention away from the argument and to another topic. This sort of "reasoning" has the following form:
Topic A is under discussion.
Topic B is introduced under the guise of being relevant to topic A (when topic B is actually not relevant to topic A).
Topic A is abandoned.
This sort of "reasoning" is fallacious because merely changing the topic of discussion hardly counts as an argument against a claim.
slippery slope: This fallacy (domino fallacy), consists in assuming without appropriate evidence, that a particular action or even is just one, usually the first, in a series of steps that will lead inevitably to some consequence.
appeal to pity (ad misericordiam): (also known as appeal to sympathy)
1. I'm positive that my work will meet your requirements. I really need the job since my grandmother is sick
2. I should receive an A in this class. After all, if I don't get an A I won't get the fellowship that I want.
I really deserve an A on this paper, professor. Not only did I study during my grandmother’s funeral, I also passed up the heart transplant surgery, even though that was the first matching donor in three years.
appeal to force (ad baculum): It is committed when instead of trying to disprove the truth of what is asserted, one uses force and, by extension, threats of force to "win a debate."
straw man: This fallacy consists in misrepresenting an opponent's point of view or argument, usually for the purpose of making it easier to attack.
is-ought fallacy: Because something is now the practice, it ought to always be the practice. Or if something is not now the practice, it ought not to be.
ad hominem: Instead of trying to disprove the truth of what is asserted, one attacks the person who made the assertion.
resort to ridicule: Consists in intruding humor or ridicule into an argument in an effort to cover up an inability or unwillingness to respond appropriately to an opponent's position.
tu quoque: (also known as appeal to hypocrisy) Defending an error in one's reasoning by pointing out that one's opponent has made the same error.
false analogy:
false dichotomy: (also known as black-and-white thinking or false dilemma)
1. Either claim X is true or claim Y is true (when X and Y could both be false).
2. Claim Y is false.
3. Therefore claim X is true.
1. Affirmative action originated as a system to overcome the effects of years of prejudice against minorities. But it has created discrimination against the majority. I
favor eliminating affirmative action requirements and returning to the old system. For all its imperfections, it's far better than what we have now.
2. You are either with us or against us.
Don’t give me that, “Jesus was just a good teacher” crap. As C.S. Lewis says, Jesus was either "Lord, lunatic, or liar."
Either restrictions must be placed on freedom of speech or certain subversive elements in society will use it to destroy this country. Since to allow the latter to occur is unconscionable, we must restrict freedom of speech.
The conclusion above is unsound because
A) subversives do not in fact want to destroy the country
B) the author places too much importance on the freedom of speech
C) the author fails to consider an accommodation between the two alternatives
D) the meaning of freedom of speech has not been defined
E) subversives are a true threat to our way of life
When workers do not find their assignments challenging, they become bored and so achieve less than their abilities would allow. On the other hand, when workers find their assignments too difficult, they give up and so again achieve less than what they are capable of achieving. It is, therefore, clear that no workers full potential will ever be realized.
Which one of the following is an error of reasoning contained in the argument?
A) mistakenly equating what is actual and what is merely possible
B) assuming without warrant that a situation allows only two possibilities
C) relying on subjective rather than objective evidence
D) confusing the coincidence of two events with a causal relation between the two
E) depending on the ambiguous use of a key term
To score in the ninetieth percentile on the SAT, one must study hard. If one studies four hours a day for one month, she will score in the ninetieth percentile. Hence, if a person scored in the top ten percent on the SAT, then she must have studied at least four hours a day for one month.
Which one of the following most accurately describes the weakness in the above argument?
A) The argument fails to take into account that not all test-prep books recommend studying four hours a day for one month.
B) The argument does not consider that excessive studying can be counterproductive.
C) The argument does not consider that some people may be able to score in the ninetieth percentile though they studied less than four hours a day for one month.
D) The argument fails to distinguish between how much people should study and how much they can study.
E) The author fails to realize that the ninetieth percentile and the top ten percent do not mean the same thing.
Of course Steve supports government sponsorship of the arts. Hes an artist. Which one of the following uses reasoning that is most similar to the above argument?
A) Of course if a person lies to me, I will never trust that person again.
B) Conservatives in the past have prevented ratification of any nuclear arms limitation treaties with the Soviet Union (or Russia), so they will prevent the ratification of the current treaty.
C) Mr. Sullivan is the police commissioner, so it stands to reason that he would support the NRAs position on gun control.
D) Following her conscience, Congresswoman Martinez voted against the death penalty, in spite of the fact that she knew it would doom her chances for reelection.
E) Youre in no position to criticize me for avoiding paying my fair share of taxes. You dont even pay your employees a fair wage.
hasty generalization: drawing generalizations from too small a sample of cases.
Sample S is taken from population P.
Sample S is a very small part of population P.
Conclusion C is drawn from sample S.
1. Smith, who is from England, decides to attend graduate school at Ohio State University. He has never been to the US before. The day after he arrives, he is walking back from an orientation session and sees two white (albino) squirrels chasing each other around a tree. In his next letter home, he tells his family that American squirrels are white.
2. Sam is riding her bike in her home town in Maine, minding her own business. A station wagon comes up behind her and the driver starts beeping his horn and then tries to force her off the road. As he goes by, the driver yells "get on the sidewalk where you belong!" Sam sees that the car has Ohio plates and concludes that all Ohio drivers are jerks.
3. A person travels through a town for the first time. He sees 10 people, all of them children. The person then concludes that there are no adult residents in the town.
4. I went to the Georgia Aquarium yesterday. All fi sh I saw there had no teeth. I bet that no fish have teeth.
My father smoked four packs of cigarettes a day since age fourteen, and lived until age sixty-nine. Therefore, smoking really can’t be that bad for you.
rationalization: using plausible-sounding but usually false reasons to justify a particular position (that is usually held on other less respectable grounds). In rationalization, the evidence comes after the belief is already accepted.
no true Scotsman fallacy:
1. Many Christians in history have started wars. Reply: Well no true Christian would ever start a war.
John: Once you accept Jesus as your savior, you will never stray from the Lord, hallelujah!
Marvin: Then why are there so many ex-Christians?
John: They were never true Christians.
Marvin: What’s a true Christian?
John: Those who have the Holy Spirit.
bandwagon fallacy (ad populum): (also known as appeal to popularity)
1. Idea X is popular.
2. Therefore, X is correct.
1. Everyone is selfish; everyone is doing what he believes will make himself happier. The recognition of that can take most of the sting out of accusations that you're being "selfish." Why should you feel guilty for seeking your own happiness when that's what everyone else is doing, too?
2. Does god exist? Several billion people can’t be wrong!
3. Seven in 10 doctors say acupuncture works; therefore, it must work
post hoc (post hoc ergo propter hoc): (also know as false cause) assuming that a particular event happens because of something because they happen at the same time.
1. Bill purchases a new PowerMac and it works fine for months. He then buys and installs a new piece of software. The next time he starts up his Mac, it freezes. Bill concludes that the software must be the cause of the freeze.
2. 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.
3. Joan is scratched by a cat while visiting her friend. Two days later she comes down with a fever. Joan concludes that the cat's scratch must be the cause of her illness.
4. Jane gets a rather large wart on her finger. Based on a story her father told her, she cuts a potato in half, rubs it on the wart and then buries it under the light of a full moon. Over the next month her wart shrinks and eventually vanishes. Jane writes her father to tell him how right he was about the cure.
special pleading: applying principles, rules, or criteria to another person while failing to apply them to oneself or to a situation that is of special interest without providing sufficient reason to support such an exception.
1. Bill and Jill are married. Both Bill and Jill have put in a full day at the office. Their dog, Rover, has knocked over all the plants in one room and has strewn the dirt all over the carpet. When they return, Bill tells Jill that it is her job to clean up after the dog. When she protests, he says that he has put in a full day at the office and is too tired to clean up after the dog.
2. Mike and Barbara share an apartment.
Mike: "Barbara, you've tracked in mud again."
Barbara: "So? It's not my fault."
Mike: "Sure. I suppose it walked in on its own. You made the mess, so you clean it up."
Barbara: "Why?"
Mike: "We agreed that whoever makes a mess has to clean it up. That is fair."
Barbara: "Well, I'm going to watch TV. If you don't like the mud, then you clean it up."
Mike: "Barbara..."
Barbara: "What? I want to watch the show. I don't want to clean up the mud. Like I said, if it bothers you that much, then you should clean it up."
3. The law requires everyone to follow the speed limit and other traffic regulations, but in Suffolk County, exceptions should be made for cops and their families, police union officials say.
Police Benevolent Association president Jeff Frayler said Thursday it has been union policy to discourage Suffolk police officers from issuing tickets to fellow officers, regardless of where they work.
"Police officers have discretion whenever they stop anyone, but they should particularly extend that courtesy in the case of other police officers and their families," Frayler said in a brief telephone interview Thursday. "It is a professional courtesy."
appeal to ignorance: (also known as shifting the burden of proof) arguing that a claim is true because there is no evidence to suggest otherwise.
Since no one has been able to prove Gods existence, there must not be a God.
Astronomers have created a mathematical model for determining whether life exists outside our solar system. It is based on the assumption that life as we know it can exist only on a planet such as our own, and that our sun, which has nine planets circling it, is the kind of star commonly found throughout the universe. Hence it is projected that there are billions of planets with conditions similar to our own. So astronomers have concluded that it is highly probable, if not virtually certain, that life exists outside our solar system. Yet there has never been detected so much as one planet beyond our solar system. Hence life exists only on planet Earth.
Which one of the following would most weaken the above argument?
A) Thousands of responsible people, people with reputations in the community to protect, have claimed to have seen UFOs. Statistically, it is virtually impossible for this many people to be mistaken or to be lying.
B) Recently it has been discovered that Mars has water, and its equatorial region has temperatures in the same range as that of northern Europe. So there may be life on Mars.
C) Only one percent of the stars in the universe are like our sun.
D) The technology needed to detect planets outside our solar system has not yet been developed.
E) Even if all the elements for life as we know it are present, the probability that life would spontaneously generate is infinitesimal.
appeal to moderation: (also known as fallacy of the golden mean, middle ground fallacy)
1. Position A and B are two extreme positions.
2. C is a position that rests in the middle between A and B.
3. Therefore C is the correct position.
1. Some people claim that God is all powerful, all knowing, and all good. Other people claim that God does not exist at all. Now, it seems reasonable to accept a position somewhere in the middle. So, it is likely that God exists, but that he is only very powerful, very knowing, and very good. That seems right to me.
2. Congressman Jones has proposed cutting welfare payments by 50% while Congresswoman Shender has proposed increasing welfare payments by 10% to keep up with inflation and cost of living increases. I think that the best proposal is the one made by Congressman Trumple. He says that a 30% decrease in welfare payments is a good middle ground, so I think that is what we should support.
3. A month ago, a tree in Bill's yard was damaged in a storm. His neighbor, Joe, asked him to have the tree cut down so it would not fall on Joes new shed. Bill refused to do this. Two days ago another storm blew the tree onto Joe's new shed. Joe demanded that Joe pay the cost of repairs, which was $250. Bill said that he wasn't going to pay a cent. Obviously, the best solution is to reach a compromise between the two extremes, so Bill should pay Joe $125 dollars.
appeal to tradition:
1. Sure I believe in God. People have believed in God for thousands of years so it seems clear that God must exist. After all, why else would the belief last so long?
2. Of course this mode of government is the best. We have had this government for over 200 years and no one has talked about changing it in all that time. So, it has got to be good.
3. Gunthar is the father of Connan. They live on a small island and in their culture women are treated as property to be exchanged at will by men.
Connan: "You know father, when I was going to school in the United States I saw that American women are not treated as property. In fact, I read a book by this person named Mill in which he argued for women's rights."
Gunthar: "So, what is your point son?"
Connan: "Well, I think that it might be wrong to trade my sisters for cattle. They are human beings and should have a right to be masters of their own fate."
Gunthar: "What a strange and new-fangled notion you picked up in America. That country must be even more barbaric then I imagined. Now think about this son. We have been trading women for cattle for as long as our people have lived on this island. It is a tradition that goes back into the mists of time. "
Connan: "But I still think there is something wrong with it."
Gunthar: "Nonsense my boy. A tradition this old must be endorsed by the gods and must be right."
4. A reporter is interviewing the head of a family that has been involved with a feud with another family.
Reporter: "Mr. Hatfield, why are you still fighting it out with the Mcoys?"
Hatfield: "Well you see young man, my father feuded with the Mcoys and his father feuded with them and so did my great grandfather."
Reporter: "But why? What started all this?"
Hatfield: "I don't rightly know. I'm sure it was the Mcoys who started it all, though."
Reporter: "If you don't know why you're fighting, why don't you just stop?"
Hatfield: "Stop? What are you crazy? This feud has been going on for generations so I'm sure there is a darn good reason why it started. So I aim to keep it going. It has got to be the right thing to do. Hand me my shooting iron boy, I see one of those Mcoy skunks sneaking in the cornfield."
faulty analogy: assuming that because two things are alike in one or more respects, they necessarily are alike in some other aspect. Those who commit this fallacy overlook the possibility of significant differences in the compared cases.
Texas sharpshooter fallacy:
circular reasoning: asserting, in one of the premises of an argument, what is asserted in the conclusion of the argument.
The death penalty is appropriate for traitors because it is right to execute those who betray their own country and thereby risk the lives of millions.
This argument is circular because right means essentially the same thing as appropriate. In effect, the writer is saying that the death penalty is appropriate because it is appropriate.
Democracy is the best form of government yet created. Therefore, we must be vigilant in its defense; that is, we must be prepared to defend the right to freedom. Because this right is fundamental to any progressive form of government, it is clear that democracy is better than any other form of government.
Which one of the following illustrates the same flawed reasoning as found in the passage?
A) I never get a headache when I eat only Chinese food, nor when I drink only wine. But when I eat Chinese food and drink wine, I get a headache. So the combination of the two must be the cause of my headaches.
B) The two times I have gone to that restaurant something bad has happened. The first time the waiter dropped a glass and it shattered all over the table. And after the second time I went there, I got sick. So why should I go there againsomething bad will just happen again.
C) I would much rather live a life dedicated to helping my fellow man than one dedicated to gaining material possessions and seeing my fellow man as a competitor. At the end of each day, the satisfaction of having helped people is infinitely greater than the satisfaction of having achieved something material.
D) Im obsessed with volleyball; thats why I play it constantly. I train seven days a week, and I enter every tournament. Since Im always playing it, I must be obsessed with it.
E) In my academic studies, I have repeatedly changed majors. I decide to major in each new subject that Im introduced to. Just as a bee lights from one flower to the next, tasting the nectar of each, I jump from one subject to the next getting just a taste of each.
equivocation:
Individual rights must be championed by the government. It is right for one to believe in God. So government should promote the belief in God.
In this argument, right is used ambiguously. In the phrase individual rights it is used in the sense of a privilege, whereas in the second sentence right is used to mean correct or moral. The questionable conclusion is possible only if the arguer is allowed to play with the meaning of the critical word right.