Unit IV: Fallacies
Some of you asked if you could make copies of
slides used in class. I decided the best thing to
do was to put a version of these slides that I had
readily available on the Web. There may be
some slides here that I did not use in class, and
there may be a few slides I used in class that are
not here. And these slides are not in any
particular order. Nevertheless, I hope they will
be useful to you.
Amphiboly
Nothing is better than happiness. A ham
sandwich is better than nothing. So a ham
sandwich is better than happiness.
B is better than C. A is better than B. So A is
better than C.
It isn’t true that there is something better than
happiness. It is better to have a ham sandwich
than not to have anything. So it is better to have
a ham sandwich than to be happy.
Amphiboly
1. If you know something, then it must be true.
2. If you know Bill Clinton won the
Presidential election in, then it must be true
that Clinton won.
4. But if something must be true, then nothing
could have happened that would make it
false.
5. But since Clinton could have lost, you don’t
know that he won.
A. Necessarily (If you know something, it is
true.)
B. If you know something, then it is necessarily
true.
Equivocation
In order to be a craftsman, a person must serve
the interest of the subject matter of his or her
craft. For example, a potter must produce good
and serviceable pots and a doctor must maintain
the health of his patient. The subject matter of
ruling is the ruled. So the ruler must serve the
interests of the ruled.
A moral person is one who lives well. If a
person lives well, then he or she is happy. So a
moral person is happy.
Plato, The Republic
Complex Question
Respond the following statements by circling a
number between 1 and 5 where 5 means you
strongly agree with the statement and 1 means
you strongly disagree with the statement.
1. Bill Clinton’s unethical involvement in the
Whitewater business deal is a good reason to
vote against him.
2. We should pass a Constitutional amendment
to stop the murder of unborn babies.
3. This is an excellent course.
Appeal to Authority
It is a fallacy to accept some claim because a
putative authority has been cited in support of
the claim if the person cited is really not an
authority in the matter at hand.
But an appeal to authority can constitute a
fallacy even when the authority really is an
authority in the matter at hand. This happens
when one refuses to consider any evidence for a
claim just because some authority rejects the
claim.
Example: Galileo claims to have seen bodies
revolving around Jupiter. On this and other
supposed evidence, Copernicus concludes that
the planets, including the earth, revolve about
the sun. This is surely false. Aristotle, Ptolemy,
and other authorities on natural philosophy say
the earth is the center of the universe and all
heavenly bodies move about it.
Alternative names for fallacies
Appeal to the people, popular sentiment,
ad populum
Appeal to emotion, appeal to sympathy,
ad misericordiam
Appeal to force, ad bacculum
Attack on the person, ad hominem
False cause,
post hoc, ergo propter hoc
False dichotomy, false dilemma
Weak analogy, false analogy
Fallacies of Relevance
Argument from Ignorance
Appeal to Authority
Argument Against the Person (ad hominem)
Appeal to the People (to Emotion)
Appeal to Pity
Appeal to Fear (to Force)
Fallacies of Presumption
(Unwarranted Assumption)
Complex Question
False Cause
Begging the Question (Circular Argument)
Accident
Hasty Generalization (Converse Accident)
Inadequate Sample
Inappropriate or Atypical Sample
False Dilemma
Fallacies of Ambiguity
Equivocation
Amphiboly
Composition
Division
Formal Reasoning Patterns
and Formal Fallacies
Reliable:
Affirming the Antecedent
Denying the Consequent
Disjunctive Syllogism — Elimination of Cases
Hypothetical Syllogism
Constructive Dilemma — Examination of Cases
Fallacious:
Affirming the Consequent
Denying the Antecedent
Disjunctive Fallacy
Argument from Ignorance
The National Toxicology Board may take
saccharine off the list of probable cancercausing compounds. The original evidence
linking saccharine involved lab rats who
developed tumors in the bladder. Researchers
now think the saccharine precipitated in the rats’
bladders as crystals and that the crystals irritated
the bladder and caused the tumors. Humans do
not consume saccharine in sufficient amounts to
produce the crystals, and no study on humans
has shown a link between saccharine and
cancer. But opponents argue that just because
saccharine does not produce cancer in humans
through one mechanism, we don’t know that it
doesn’t produce cancer in humans through
another mechanism. Thus, they say, saccharine
should not be ‘delisted’.
National Public Radio, Oct. 30, 1997
Complex Question
This is an example of a valid survey question.
Which of the following best represents your
attitude toward Clinton’s deposition in the Paula
Jones case.
A. He committed perjury and should have been
removed from office.
B. He committed perjury and should have been
censured, but not removed from office.
C. If he committed perjury, it was only about
his personal sex life and isn’t that important.
D. He didn’t commit perjury.
E. No opinion.
Complex Question
This survey question commits the fallacy.
Which of the following best represents your
attitude toward Clinton’s perjury in the Paula
Jones case.
A. He should have been removed from office.
B. He should have been censured, but not
removed from office.
C. It’s not that important and it has already
received too much attention.
D. No opinion.
Rhetorical Question
During the period 1987-1997, the University
saw tremendous improvement in its facilities.
New buildings included the Biological Sciences
Center, the additions to the law school and the
business school, and all of east campus
including a new Student Health Center, an
Animal Sciences Building, the Fine Arts
Complex, the Ramsey Student Activity Center,
and the East Parking Deck. And who was
President of the University during this period?
We owe Dr. Charles Knapp a big “Thank you!”
False Cause
My car misfires whenever I buy gas from the
station on the corner. It never misfires when I
buy gas somewhere else. I think the gas at the
corner station causes my car to run badly.
Since I started giving Mary a ride to school
everyday, my car has been misfiring. I think
Mary causes my car to run badly.
Begging the Question
(Circular Argument)
Women should not get abortions because an
unborn fetus is nevertheless a person, and
destroying the life of any person is wrong.
Women should not get abortions because it is
wrong to terminate a viable fetus.
Accident
Birds fly. John’s new pet is a bird. So John’s
new pet can fly.
Birds fly. John’s new pet is a penguin, and
penguins are birds. So John’s new pet can fly.
Bob was late for class. So he parked in a
handicap space. He should be given a ticket.
That woman in a wheelchair parked in a
handicap space. She should be given a ticket.
Hasty Generalization
Which one is a fallacy and why?
The CDC conducted a study of people with high
cholesterol. They randomly divided them into
two groups of 100. One group was given a
cholesterol-lowering medication for ten years
and the other was given a placebo for the same
period. At the end of the study, the group taking
the medication had experienced 45% fewer
heart attacks. These new drugs are an effective
weapon in fighting heart disease.
The CDC studied two people with high
cholesterol. One person was given a cholesterollowering medication for ten years and the other
was given a placebo for the same period. At the
end of the study, the person taking the
medication had experienced 45% fewer heart
attacks. These new drugs are an effective
weapon in fighting heart disease.
Hasty Generalization
(Atypical Sample)
Americans overwhelmingly support access to
abortions for women. The National
Organization for Women recently conducted a
survey of its 250,000 members. Over 90%
responded to the questionnaire distributed by
NOW, and over 90% of those responding said
safe, legal abortions should be available to
women who want them.
False Dilemma
If you go to college, you’ll depend on your
father for tuition and living expenses. If you
work for your father’s company, you will
depend upon your father for your salary. You
can either work for your father’s company or go
to college. So you are going to remain
dependent on your father.
If you study, you won’t have time to party. If
you don’t study, your parents will cut off your
allowance and you won’t have the money to
party. Either you study or you don’t. So college
isn’t going to be as much fun as you thought.
Smith either stays away from his former partner
in crime, Jones, or he violates the conditions of
his parole. If he violates parole, he will go back
to prison. He doesn’t want to go back to prison;
so Smith should stay away from Jones.