Logical Fallacies
 Hasty Generalizations: occur when we assert that a conclusion is true
based on insufficient evidence…either the statistical sampling is too small, or
the general principle is incorrect.
– Two students in class told me they voted for Ms. Smith…I know she is gonna win Teacher
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of the Year.
I ate some bad tuna last week: I won’t ever eat tuna fish again because it is often rotten.
 Stereotypes: a Hasty Generalization made regarding a group of people.
– All Ursuline girls are stuck up.
 Post Hoc Ergo Propter Hoc: “before the fact therefore because of the fact.”
Whenever someone asserts or implies that an event that occurred before
another event must have caused that event. Another name for this is “Faulty
Cause and Effect.” Many superstitions have their basis in this fallacy.
– Inflation tripled after Jimmy Carter was elected President. His policies must have been
inflationary.
– After Sweden lifted restrictions on pornography, instances of violent sexual crime
decreased; this proves that restrictions on pornography rather than pornography itself
causes sexual crimes.
– Yesterday afternoon it rained, Yesterday afternoon I failed m y math test. I failed my math
test because it rained yesterday.
 The Either/Or fallacy is a variation on the post hoc fallacy. It asserts that a
conclusion will occur only if a specific action is taken; or unless an action is
taken, only one result will occur. This fallacy ignores the possibility of
alternative solutions.
– Every year, when the asphalt starts to get stick y, people die of heat stroke. W e must fix the
asphalt or people will continue to die of heat stroke..
– A recent study by a prominent researcher showed that elementary-school students who
live in houses without central air conditioning do poorer on standardized tests than children
live in houses with central air conditioning. There seems to be something about central air
conditioning that is conducive to learning. Therefore equipping every house with airconditioning will raise test scores.

Begging the Question: the arguer somehow, often very subtly, asserts, as
truth, the answer to a question that is really at issue in the debate and then
uses the resulting, faulty premise as the basis for further debate or
argumentation. Another name for this fallacy is “Circular Reasoning.”
– The reason that abortion is wrong is that it is wrong to kill babies who don't have any
change to represent themselves. (The question that is "begged" is whether or not a fetus is
a "baby," which is an integral part of the debate.)
– Of course guns should be outlawed. Anything that dramatically increases the number of
deaths of young people in this country should be outlawed. (The question of whether or not
gun ownership does dramatically increase the numbers of deaths of young people is very
much at issue in the debate over guns.)
– Shakespeare is a better writer than Spenser because he more closely duplicates real life
experiences. (This assumes that real life experiences have more literary value than
fantasy.)

Ad Hominem: meaning "against the man." In this fallacy you are attacking a
person, not an issue. This fallacy should not be confused with simple name
calling; realize also it is not a fallacy to legitimately challenge an authority. If
someone asserts a point based on their own authority, then it is very logical to
call that authority into question. This fallacy asserts that someone's argument
or viewpoint should be discounted because of character flaws that have
nothing to do with the arguments.
– How can people believe the theory of evolution when it is a well-known fact that Darwin
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cheated on his wife?
Free trade must be a bad idea; it is advocated by both Senator Hansen and
Representative McGuire, both of whom have admitted to using marijuana in college.
The problems with hip-hop music can be summed up with two names: Notorious B.I.G. and
2Pac Shakur--two big hip-hop stars who died senseless, violent deaths
Unqualified Authority : an argument is asserted as true on the sole grounds
of its endorsement by an authority, or perceived authority, figure. Expert
testimony is not a fallacy; it is good reasoning. However, such appeals
become fallacious: 1) when the authority figure does not have any expertise in
the area under discussion; 2) when opposite opinions of other authorities are
suppressed; or 3) when the testimony of the authority figure is given
disproportionate weight in relation to other considerations.
–
Eat W heaties cereal so you can be like Michael Jordan (Michael Jordan is an excellent
authority figure for advice on basketball; a much more limited one for advise on nutrition)
– The existence of life the fourth moon of Saturn is proven by the fact that Dr. Martin
Finkleberry, who received a Ph.D. from Cal Tech., believes absolutely that it is inhabited by
large, intelligent blobs of jelly. (Dr. Finkleberry may well believe it, but most experts on the
subject do not).
– W e should not allow "science" to blind us to truth. Both the Bible and the works of Aristotle
tell us that the earth moves around the sun. That settles it (This, roughly, was the
argument used by the Church to force Galileo to recant his beliefs despite overwhelming
evidence to the contrary).
 Appeal to emotions—manipulates people's emotions in order to get their
attention away from an important issue.
– Bandwagon—creates the impression that everybody is doing it and so should you
– False dilemma—limits the possible choices to avoid consideration of another choice
– Appeal to the people—uses the views of the majority as a persuasive device
– Scare tactic—creates fear in people as evidence to support a claim.
The Persuasive Essay
 Utilizes logic and reason to show that one idea is more legitimate than another idea. It
attempts to persuade a reader to adopt a certain point of view or to take a particular action.
The argument must always use sound reasoning and solid evidence by stating facts, giving
logical reasons, using examples, and quoting experts.
W hen planning a persuasive essay, follow these steps
1. Choose your position. W hich side of the issue or problem are you going to write about,
and what solution will you offer? Know the purpose of your essay.
2. Analyze your audience. Decide if your audience agrees with you, is neutral, or disagrees
with your position.
The following criteria are essential to produce an effective argument:
.
Persuasive Essay cont.
 3. Research your topic. A persuasive essay must provide specific
and convincing evidence. Often it is necessary to go beyond your
own knowledge and experience. You might need to go to the library
or interview people who are experts on your topic.
4. Structure your essay. Figure out what evidence you will include
and in what order you will present the evidence. Remember to
consider your purpose, your audience, and you topic.
Persuasive Essay Cont.
 5. Be well informed about your topic. To add to your knowledge
of a topic, read thoroughly about it, using legitimate sources. Take
notes.
 6.Test your thesis. Your thesis, i.e., argument, must have two
sides. It must be debatable. If you can write down a thesis
statement directly opposing your own, you will ensure that your
own argument is debatable.
.
Persuasive Essay cont.
 7.Disprove the opposing argument. Understand the opposite viewpoint of
your position and then counter it by providing contrasting evidence or by
finding mistakes and inconsistencies in the logic of the opposing argument.
 8. Support your position with evidence. Remember that your evidence must
appeal to reason. The following are different ways to support your argument:
Facts - A powerful means of convincing, facts can come from your reading,
observation, or personal experience.
Persuasive Essay cont.
 Note: Do not confuse facts with truths. A "truth" is an idea believed
by many people, but it cannot be proven.
Statistics - These can provide excellent support. Be sure your
statistics come from responsible sources. Always cite your sources.
Quotes - Direct quotes from leading experts that support your
position are invaluable.
Examples - Examples enhance your meaning and make your
ideas concrete. They are the proof