Rhetorical / Logical Fallacies
What is an Argument?
• An argument must be based on sound
reasoning
• There are two important components to an
argument: premises and conclusion
– Premise: an assertion that will support a
conclusion (i.e. evidence)
• The most important part of any premise is that your
audience will accept it as true.
• If your audience rejects even one of your
premises, they will likely also reject your
conclusion, and your entire argument will fall apart
– Conclusion: the logical concept, based upon
premises, that is being asserted
• Audience may not have to accept a conclusion as
true
• Evidence will try to persuade the audience of a
conclusion’s truth
• A thesis statement is a conclusion.
Validity and Soundness
• Validity
– an argument is considered valid if its
construction ensures that, if the premises
were to be true, the conclusion necessarily
must be true.
– The premises do not actually have to be true
for an argument to be valid. The argument’s
construction simply means that if the
premises are true, the conclusion cannot be
false.
– Example: Valid and true premises
Either Elizabeth owns a Honda or she owns a
Saturn.
Elizabeth does not own a Honda.
Therefore, Elizabeth owns a Saturn.
– Example: Valid but untrue premises
All toasters are items made of gold.
All items made of gold are time-travel devices.
Therefore, all toasters are time-travel devices.
• Soundness
– an argument is considered sound if it is both
valid and uses premises that are actually true.
– Example:
No felons are eligible voters.
Some professional athletes are felons.
Therefore, some professional athletes are not
eligible voters.
What is a Fallacy?
• Fallacies are flaws in reasoning that
detract from the validity and/or soundness
of an argument
• Sometimes their use is by accident;
others, they are used to deliberately
mislead or “win” an argument
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.”
What’s wrong with this line of
reasoning?
Answer: The argument is fallacious because
it falsely assumes that since the one thing
(eating five candy bars) immediately
precedes the other (getting an A), the
relationship is causal.
Why Can Fallacies Be Difficult
to Identify?
• Some fallacious arguments actually are
valid, but not sound.
• Many arguments can be difficult to parse,
i.e. break down into core premises
• Many people actually are persuaded by
fallacious arguments, and might believe
them to be sound and/or true when they
really aren’t.
Categories of Rhetorical Fallacies
Since there are three primary argumentative
modes, there are three categories of fallacies:
• Logical (Logos) – Flaws in logical reasoning
• Ethical / Authoritative (Ethos) – Appealing to
authority or morality on its own terms
• Emotional (Pathos) – Trying to manipulate
emotionally or to scare people
Fallacies of Logic
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Hasty Generalization
Post Hoc
Non sequitur
Equivocation
Begging the Question
Faulty Analogy
Stacked Evidence
Appeal to Ignorance
Hasty Generalization
• Conclusion is drawn based on little or
insufficient evidence
• Example: “That restaurant’s food is terrible! I
ate there once and my food was
undercooked.”
• Why is this fallacious?
Post Hoc, Ergo Propter Hoc
• Latin for “after this, therefore because of this”
• Assumes that because an event happens before
another event, that the first event actually
causes the second
• Also known as false cause fallacy
• Example: “A year after the release of the violent
shoot-’em-up video game Annihilator, incidents
of school violence tripled… surely not a
coincidence.”
• Why is this fallacious?
Non sequitur
• Latin for “it doesn’t follow”
• Argument does not follow any sort of logical
sequence
• Example: “It rained so hard that Jenn
actually called me!”
• Example: “My dog got so sick that my
grandma made stew.”
• What’s wrong with these arguments?
Equivocation
• Commonly referred to as “half-truths”
• A partially correct statement that tries to
hide behind double meanings
• Example: “I did not have sexual relations
with that woman.” – Former President Bill
Clinton
Begging the Question
• Circular argument
• The premise and the
conclusion are the
same thing stated
differently
• Example: “His lies are
evident from the
untruthful nature of
his statements.”
Faulty Analogy
• An inaccurate, inappropriate comparison
between two things
• Example: “Forcing students to attend
cultural events is like leading cattle to
slaughter.”
Stacked Evidence
• Distorts an issue by overwhelmingly supporting
or representing only one part of it
• Usually done intentionally to make one
particular part of an issue appear clearly
favorable to the others
• Example: “Cats are superior to dogs because
they are cleaner, cuter, and smarter.”
Appeal to Ignorance
• Asserts that since an argument cannot be
disproven, it therefore is true
• Burden of proof always rests with the
affirmative
• Example: “Aliens exist because you cannot
prove that they don’t.”
Ethical / Authoritative Fallacies
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False Authority
Authority as Evidence
Guilt by Association
Dogmatism
Ad Hominem
Strawman
False Authority
• Claims that an assertion is true based
solely on the person who made the
assertion
• Example: “Mr. King says that the sky is
red, and Mr. King is smart, so it must be
true.”
Authority as Evidence
• A speaker uses his or her own authority to
prove that a claim is true
• Usually such claims are totally unrelated to
the speaker’s own expertise
• Example: “Dr. Pepper is smooth. Trust me –
I’m a doctor.”
• Example: “My friend would never rob a bank.
Trust me.”
Guilt by Association
• Assumes that an
argument is true
because the person
involved is associated
with someone or
something negative
• Example: “Tom’s
friend robbed a bank,
so Tom is a bad
person.”
Dogmatism
• A claim is assumed true because the speaker
believes it to be true
• Otherwise known as “because I said so”
• Example: “Penguins are reptiles, and that’s
that.”
Ad Hominem
• Instead of debating an issue, the speaker
attacks the person who makes a competing
claim
• Often seen in political campaigns
• Example: “How can we trust Ms. Ware to run
the city when she can’t even handle her own
marriage?”
• Example: “Senator Kelly’s plan is terrible
because Kelly is a communist.”
Strawman
• A speaker misrepresents
or oversimplifies an
opposing view in order to
tear it down
• Example:
– Will: “We should put more
money into health and
education.”
– Warren: “I am surprised
that Will hates our country
so much that he wants to
leave it defenseless by
cutting military spending.”
Emotional Fallacies
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Red Herring
Scare Tactics
Bandwagon (Ad Populum)
Slippery Slope
Either / Or
Appeal to Pity
Red Herring
• An irrelevant distraction,
attempting to mislead an
audience by bringing up
an unrelated, but usually
emotionally loaded issue.
• "In regard to my recent
indictment for corruption,
let’s talk about what’s
really important instead-terrorists are out there,
and if we don't stop
them we're all gonna
die!"
Scare Tactics
• Tries to manipulate people’s fears to sway
their decisions
• Example: “If you don’t vote for Deutscher for
President, the economy will implode and your
family will starve.”
Bandwagon
• Also known as “Ad
Populum”
• Implies that a choice is
correct because it is
popular
• Often used in
advertising – celebrity
spokesperson
• Example: “Five million
Coke drinkers can’t be
wrong!”
Slippery Slope
• Argues that one thing automatically will lead
to another – usually with disastrous results
• The cause and effect relationship often is
completely exaggerated or absurd
• Example: “If we allow gay marriage, then
people will start practicing polygamy and
marrying their pets, and the fabric of society
will crumble.”
Either / Or Choices
• Setting up a false dichotomy for an issue
• Inaccurately reduces an issue to two possible
outcomes
• Usually one outcome is absurd and the other
is infinitely favorable
• Example: “You can either approve the new tax
plan or you can say goodbye to adequate
emergency services!”
Appeal to Pity
• Using feelings of sympathy or sorrow to
convince someone
• Making the audience feel sorry for someone is
not by itself a sufficient argument
• Example: “I’ve been having such a hard time
recently, Mr. King. My printer broke, my cat
died – twice – and I got grounded. Please just
give me an A on the paper.”
For More Information…
• http://writingcenter.unc.edu/handouts/fallacies
• This is an excellent resource providing
explanations and examples of the various
types of rhetorical fallacies
• We also will look at numerous examples and
applications of rhetorical fallacies in class.