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Fallacies Exercises for Critical Thinking
Critical Reading, Writing and Thinking (De Anza College)
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Fallacy - an error in reasoning that is psychologically persuasive, or a misleading type of argument.
Each fallacy breaks at least one rule for good arguments. We commit fallacies
The textbook lists them all alphabetically then breaks them into two groups in the exercises. We are
going to break them into three groups and go just a bit slower in learning them. The internet is full of
resources for learning more about fallacies (some of those resources are better than others). There’s
some debates about the titles and definitions or just how many fallacies there are1, so you’ll see different
lists than this one other places. Those debates shouldn’t present any problems for us learning these
sixteen fallacies (20 are named, but two are formal fallacies and two are just other ways of naming a
fallacy on the list). And you’re responsible only for what is in our textbook.
Fallacies of Relevance: when the premises are not relevant to the conclusion. In one sense, any fallacies of
relevance could be categorized as a non sequitor , which is just Latin for “it does not follow from.”
Ad Hominem: attacks the person arguing, not the argument. The character, characteristics, affiliations, or
behaviors of the individual making the argument is logically irrelevant to the truth or falsity of what the person
says, or to the correctness or incorrectness of that person's reasoning. Sometimes you’ll see a version of this
named Tu Quoque – that’s latin for “you’re another”, that’s the charge of hypocrisy. Later you’ll see the version of
this fallacy that is based on name calling (poisoning the well).
Even though we can, and we usually should, dismiss expert sources that are biased – see rule 15 – we do so by
pointing out the bias and how it has affected their reasoning, not by attacking their person.
Atheism is an evil philosophy.
murderers.
It is practiced by Communists and
It is perfectly acceptable to kill animals for food. How can you argue
otherwise when you're quite happy to wear leather shoes?
You're telling me I should drink less? You haven't been sober in a year.
Ad Ignoratniam - Argument from Ignorance: argue that a proposition is true merely because it has not been
proven false, or that it is false merely because it has not been proven true. This is a jumping to conclusions
problem.
The exception would be the judicial system: Innocent until proven guilty.
If there really were a large and unusual type of animal in Loch Ness, then we
would have undeniable evidence of it by now.
We don't have undeniable evidence of a large, unfamiliar animal in Loch Ness.
Therefore, there is no such animal.
Ad Misericordiam - Appeal to Pity: special emotional appeal to mercy and altruism
I did murder my mother and father with an axe, but please be lenient in
sentencing because I'm suffering enough through being an orphan.
1 If you’re interested, I – along with a friend – have baptized a new fallacy that we think more logic textbooks should include. The article
is available online right now and should be in print next month.
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Ad Populum - Appeal to the People: bandwagon or vanity, appealing to the emotions of a group
The Bible must be true. Millions of people know that it is.
to tell them that they are all mistaken fools?
Are you trying
Most Advertising!!!
Red Herring – diverts attention away from the original point by introducing an irrelevant point. These work when
someone introduces a point that is similar or even related to the main point, but is still not the main point. They
also work when the red herring is controversial and people get distracted by the seeming urgency or significance
of the matter despite it being irrelevant.
The origins of this title are a bit fuzzy but it seems to come from fox hunting. People would drag smoked herring
(thus they were red) to distract dogs on the hunt (maybe for the fun of extending the hunt, maybe as anti-hunting
distractions, maybe people did it to distract wolves from hunting them).
Andy Taylor says: “Hey, what's with all this junk food you bought? You're
always pestering me about eating healthy." Aunt Bea replies: "Don't fuss,
Andy, it was on sale."
Straw Man - presenting an exaggerated, usually oversimplified, version of the view you are disagreeing with in
order to easily defeat it.
Breaking Rule 5, or using overtone instead of substance, often results in straw man fallacies.
I can’t believe sex education is mandatory in Fresno Unified again! These
proponents of sex education want to give kids license to have sex with no
consequences.
EXERCISES: Identify the fallacy of relevance being committed in the following short arguments. Give
the name. Try also to give a brief description of the error.
1. Discipline is important in education. Rousseau opposed discipline, but he was a pervert.
2. Animal rights activists say that animals are abused in biomedical research labs. But consider this:
Pets are abused by their owners every day. Probably 25% of pet owners should never get near
animals. Some cases of abuse are enough to make you sick.
3. Of course telepathy and other psychic phenomena do not exist. Nobody has shown any proof that
they are real.
4. Senator Thorpe says an arms limitation treaty would be dangerous. But he's from a state that
produces planes and missiles.
5. I am qualified for the job - I have some experience and I really need the money. So, hire me.
6. The school board argues that our schools are in desperate need of repair. But the real reason our
students are falling behind is that they spend too much time with their computers. Becoming
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educated means a lot more than learning how to point and click. The school board should send a
letter to the parents urging them to monitor their kids’ computer time.
7. Clarence Darrow’s plea to a jury, as cited in Stone, Clarence Darrow for the Defense, 1943:
You folks think we city people are all crooked, but we city people think you farmers are all
crooked. There isn’t one of you I’d trust in a horse trade, because you’d be sure to skin me. But
when it comes to having sympathy with a person in trouble, I’d sooner trust you folks than city
folks, because you come to know people better and get to be closer friends.
8. People who believe we should spend less for defense apparently believe no one will ever attack us.
9. How can you possibly be a Seahawks fan? Everyone around here is a 49ers fan!
10. Of course you would argue that positive discrimination is a bad thing. You're white.
11. You should support the new housing bill. We can't continue to see people living in the streets; we
must have cheaper housing.
12. Dr. Morrison has argued that smoking is responsible for the majority of health problems in this
country and that every smoker who has even the slightest concern for his or her health should quit.
Unfortunately, however, we must consign Dr. Morrison’s argument to the trash bin. Only yesterday I
saw none other than Dr. Morrison himself smoking a cigar.
13. No one has proved conclusively that America’s nuclear power plants constitute a danger to people
living in their immediate vicinity. Therefore, it is perfectly safe to continue to build nuclear power
plants near large metropolitan centers.
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Fallacies of Presumption: to assume the truth of some unproved and unwarranted proposition, which is then used
to support the conclusion.
Begging the Question or Petitio Principii (Circular Reasoning): to assume the truth of what one seeks to prove, in
the effort to prove it
Communists must not be allowed to hold government office. Hence any
government official who is revealed to be a communist will lose his job.
Therefore communists will do anything to hide their secret, and will be open
to blackmail. Therefore communists cannot be allowed to hold government
office.
We know that God exists because the Bible tells us so.
Bible is true because it is the word of God.
And we know that the
Complex Question: to ask a question in a way to presuppose the truth of some conclusion buried in the question:
often rhetorical. But, this is also used in legal situations when the questioner insists you can only give a simple
yes-or-no answer, neither of which would suffice.
Have you stopped beating your wife?
Does the Chancellor plan two more years of ruinous privatization?
False Dilemma or Overlooking / Ignoring Alternatives: presenting the available options as if there are only two,
often clashing.
Recall that when Dilemmas (Rule 26) do this in the disjunctive premise, then that premise is bad (even if the
argument form is valid).
You can stay here or you can go home.
False Cause - drawing a wrong conclusion about a cause – effect relationship
Chapter V provided guidance for imagining possible causal explanations and then identifying the most likely one.
When you’ve found someone describing or defending a bad causal account, this is the general name for the
fallacy. Whether you choose to help identify the right one is another step in rational discussions.
post hoc ergo propter hoc - (Latin for “after the thing, therefore because of the thing”) is a specific sort of causal
error where a connection in time appears to or is taken to establish a cause
Roosters crow just before the sun rises. Therefore, roosters crowing cause the
sun to rise.
The Soviet Union collapsed after taking up atheism.
atheism for the same reasons.
Therefore we must avoid
Overgeneralizing – making too broad or too hasty a generalization.
These violate Rules 7 and 8.
Jim Bakker was an insincere Christian.
insincere.
Therefore all Christians are
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EXERCISES: Identify the fallacy of presumption being committed in the following short arguments.
Give the name. Try also to give a brief description of the error.
14. In the Miss Universe Contest of 1994, Miss Alabama was asked: If you could live forever, would
you? And why? She answered: “I would not live forever, because we should not live forever,
because if we were supposed to live forever, then we would live forever, but we cannot live forever,
which is why I would not live forever.”
15. Where did you hide the money you stole?
16. I took an aspirin and prayed to God, and my headache disappeared. So God cured me of the
headache.
17. Barbra Streisand, Paul Newman, and Julia Roberts are Democrats. Therefore, it must be the case
that all Hollywood starts are Democrats.
18. Marijuana should not be legalized for personal consumption because if there weren’t anything wrong
with it, it would already be legal, which it isn’t.
19. Look, you can either come to my party or accept that our friendship is over.
20. State Representative Ernst Istook, Jr. claimed: “As prayer has gone out of the schools, guns, knives,
drugs, and gangs have come in.” So Douglas E. McNeil, in a letter to the editor, responded: “We
could just as well say that after we threw God out of the schools, we put a man on the moon.”
21. Says the proprietor of a fish & chips shop in England about the growing concern of the relation
between consuming fried foods and dangerous cholesterol levels: “Take my son Martin. He’s been
eating fish & chips his whole life, and he just had a cholesterol test, and his level is below the
national average. What better proof could there be than a fryer’s son?”
22. A 1992 national mailing soliciting funds by the People for the Ethical Treatment of animals (PETA)
contains a questionnaire with check boxes for yes or no answers. Two of the questions asked are
these: “Do you realize that the vast majority of painful animal experimentation has no relation at all
to human survival or the elimination of disease?” and “Are you aware that product testing on
animals does not keep unsafe products off the market?”
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23. If you want a life full of sexual pleasures, don’t graduate from college. A study to be published next
month in American Demographics magazine shows that the people with the most education have the
least amount of sex.
–The Chronicle of Higher Education, 15 January
1998
24. The Daily News today carried an article about three local teenagers who were arrested on charges of
drug possession. Teenagers these days are nothing but a bunch of junkies.
25. Look, you are going to have to make up your mind. Either you decide that you can afford this stereo,
or you decide you are going to do without music for a while.
26. Two gold miners roll a boulder away from its resting place and find three huge gold nuggets
underneath. One says to the other, “Great! That’s one nugget for you and two for me,” handing one
nugget to his associate. “Wait a minute,” says the second miner. “Why do you get two and I get just
one?” “Because I’m the leader of this operation,” says the first. “What makes you the leader?” asks
miner number two. “I’ve got twice the gold you have,” answers the first.
27. After deciding to sell his home in Upland, California, novelist Whitney Stine pounded a “For Sale”
sign into his front yard. But he deliberately waited to do so until 2:22 PM one Thursday. The house
sold three days later for his asking price. And Mr. Stine credits the quick sale to the advice of his
astrologer, John Bradford, whom he has consulted for 12 years in the sale of five houses. “He
always tells me the exact time to put out the sign according to the phases of the moon, and the
houses have always sold within a few months,” Mr. Stine says.
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Fallacies of Ambiguity and Language: sophisms, when the meanings of words or phrases shift or are unclear or
where mistakes occur because of misunderstandings
Equivocation: using more than one meaning of a word in the same argument. This causes semantic ambiguity.
These break Rule 6, which requires good arguments to use terms consistently.
What could be more affordable than free software? But to make sure that it
remains free, that users can do what they like with it, we must place a
license on it to make sure that will always be freely redistributable.
In fallacy language, we call a problem of syntactic ambiguity an Amphibolv.
Women prefer Democrats to men.
Save tress and waste paper.
Some logicians add a fallacy of Accent too, when placing stress or emphasis on different words or phrases
changes the meaning; changing context or manipulating quotes
"We should not speak ILL of our friends"
and
"We should not speak ill of our FRIENDS"
Loaded Language: using language that plays on emotions, not substantial content.
These break Rule 5.
Since you don’t believe in God, you are rejecting goodness, kindness, and love
itself.
The teaser for the next news segment: Stay tuned to hear how Governor Davis
carelessly cast the deciding vote earlier today to pass both the budget bill
and the trailer bill to fund yet another excessive watchdog committee over
coastal development.
Persuasive Definition: defining a key term in a way that already presumes or secretly argues for a conclusion.
This is a precise place for loaded language.
Let's define a Democrat as a leftist who desires to overtax the corporations
and abolish freedom in the economic sphere.
Poisoning the Well: using loaded language preemptively, to set up a negative feeling about the person arguing
before even beginning an argument. These are often ad hominem attacks too.
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EXERCISES: Identify the fallacy of language being committed in the following short arguments. Give
the name. Try also to give a brief description of the error.
28. I also admit that there are people for whom even the reality of the external world [is] a grave
problem. My answer is that I do not address them, but that I presuppose a minimum of reason in my
readers.
–Paul Feyerabend, “Materialism and the Mind-Body
Problem”
29. A Worm-eating Warbler was discovered by Hazel Miller in Concord while walking along the branch
of a tree, singing, and in good view. (New Hampshire Audubon Quarterly) That’s our Hazel—
surefooted, happy, and with just a touch of the exhibitionist.
–The New Yorker, 2 July
1979
30. Thomas Carlyle said of Walt Whitman that he thinks he is a big poet because he comes from a big
country.
31. Corporations should not be allowed to advertise in classroom. This is nothing more than corporate
invasion into our children’s schools. Their insidious battle plan is working. First they tell us that
schools need more computers to prepare our children for better jobs. Then we accept these gifts that
are nothing more than Trojan horses that beat our children into complacency by ubiquitous media
bombardment.
32. Dr. Salick, donated, along with his wife, Gloria, $4.5 million to Queens College for the new research
center.
33. No man will take counsel, but every man will take money: therefore money is better than counsel.
–Jonathan
Swift
34. I think you can safely assume that Justice Scalia’s opinions on this session’s cases will be every bit
as flaky as his past opinions.
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35. The anthropologists went to a remote area and took photographs of some native women, but they
weren't developed.
36. Archbishop Richard Holloway says we should not condemn people for their adulterous affairs for
“Man was born to have many lovers.”
37. Only an idiot would consider this text to be making a rational argument. Anyone in class have any
thoughts or questions about the reading?
38. That student cannot claim he has suffered persecution for his beliefs because he is an atheist and
atheists, by definition, lack beliefs.
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More on Red Herrings and Straw Man Fallacies
Both of these are fallacies that occur when responding to another person’s argument.
They do not happen when stating a new conclusion, but when disagreeing with someone
else’s argument. And both are common mistakes when we disagree with a conclusion but
struggle to have rational disagreement with their premises or the form of the
argument. When we aren’t thinking critically but we are emotional, biased, or just
trying to win, we resort to the weakest of arguments that depend on irrelevant
points. They can be persuasive, though, because others aren’t thinking critically
either and don’t notice the slight shift in topics or positions.

In the Red Herring Fallacy, the error occurs by introducing a related or
similar topic as if it is relevant to the issue at hand when it is actually
irrelevant and off topic and distracts the argument rather than resolves it.

In the Straw Man Fallacy, the error occurs by distorting, oversimplifying, or
weakening the opponent’s position so that it can be more easily refuted. But
defeating a straw version of your opponent’s argument doesn’t make you a
winner, doesn’t mean you have defeated your opponent.
39. Bobby regularly invites people to join him at his church on Sundays, claiming that the teachings of
Christianity are undoubtedly true. He then describes at length that Christianity is of great help to many
people in hopes they will find the truth in Christianity too and save their eternal souls.
40. David says that he’s opposed to the new euthanasia laws that make it legal for consenting adults and their
doctors to employ a medical a means of terminating their lives after a diagnosis of terminal illness. Obviously,
he thinks that doctors are special and should be protected from any fault. They can just start killing people, the
old and the disabled especially. Do you want doctors everywhere prescribing lethal doses of drugs to anyone
with a cancer diagnosis? David does, and he’s dead wrong.
41. Every woman should have the right to an abortion on demand. There’s no question about it. These antiabortion activists block the entrances to abortion clinics, threaten abortion doctors, and intimidate anyone who
attempts to terminate a pregnancy.
42. The legislators should vote for the three-strikes-and-your-out crime control measure. I’m telling you, crime is
a terrible thing when it happens to you. It causes death, pain, and fear. And I wouldn’t want to wish these
things on anyone.
43. Lawyers for the ACLU have sued to remove the massive Ten Commandments monument from the lobby of
the courthouse. As usual, they are as anti-religious as ever. They want to remove every vestige of religion and
faith from American life. Don’t let them do it. Don’t let them win yet another battle in their war to secularize
the whole country.
44. A member of the organization In Defense of Animals, following a protest of Chinese markets in San
Francisco for cruelty in selling both live and slaughtered animals, wrote the following in an AP article: “The
time of the crustaceans is coming. You’d think people wouldn’t care about lobsters, because they aren’t
cuddly and fuzzy and they have these vacant looks and they don’t vocalize. But you’d be surprised how
many people care.” In response, Astell Kung, proprietor of Ming Kee Game Birds, where fowl are sold live,
wrote the following letter to the editor:
How about the homeless people? Why don’t the animal people use their energy to care for those people?
They have no homes! They are hungry!
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