Fallacies
To error in reason is human; to
analyze divine!
Logical Fallacy?
• An error of reasoning.
• When someone adopts a position, or tries to
persuade someone else to adopt a position,
based on a bad piece of reasoning.
• The following is a collection of errors of
reasoning that are
commonly used and thus
named.
Pathos
Appeal to Emotion
Think ASPCA commercials...
http://www.youtube.com/watch?v=Ae5_QkVtXdg
Ethos
Appeal to Credibility
“Trust me, I'm a doctor”
Logos
Appeal to Logic.
If A is B, and B is C, then A is C.
Man is Mortal
Socrates is a Man
Therefore, Socrates is Mortal.
Taxonomy of Fallacies
• Warning! Some fallacies are difficult to place
in any category; others belong in two or three.
Ad Hominem
• Ad Hominem arguments attack a person’s
character rather than that person’s
reasoning.
• Example: Why should we think a candidate
who recently divorced will keep his campaign
promises?
Appeal to Force:
• The writer threatens the audience, explicitly
or implicitly, with negative consequences if
the claim is not believed.
• Example: If you do not believe in God, you will
go to hell.
Appeal to Pity
• The writer begs for the
approval of the
claim; the audience
may agree because
they feel sorry for the
arguer.
• I cannot get a job
because the public
education system failed
me; I have to steal
to survive. It is
society's fault, not
mine.
Appeal to Authority
• The writer cites authorities to
show the validity of the claim, but
the authority is not an expert in
the field, the authority's view is
taken out of context, or other
experts of that field disagree with
the authority quoted.
• I think that businesses should not
have to limit the amount of
pollutants they release into the
atmosphere because Rush
Limbaugh says that there is no
real evidence for industrial
pollutants causing the Greenhouse
Effect.
Post hoc ergo propter hoc
• Post hoc ergo propter hoc, Latin for "after this,
therefore because of this", is a logical fallacy that
states, "Since that event followed this one, that
event must have been caused by this one.“
• More and more young people are attending high
schools and colleges today than ever before. Yet
there is more juvenile delinquency and more
alienation among the young. This makes it clear
that these young people are being corrupted by
their education.
https://www.youtube.com/watch?v=vRJUvFG8gbE
Appeal to the Popular or
Bandwagon
• The writer bases the argument on the belief
that if an idea is held by a large group of
people, it is true.
• Millions of people are Marxists, so Marxist
economic and political theories are correct.
Appeal to Tradition
• The writer relies on traditional wisdom to support
the argument. This is a logical pitfall because the
argument does not consider that new ideas could
apply.
• People have believed that fish is "brain food" for
decades, so I don't believe the FDA when they claim
that eating fish does not enhance the intellect.
Begging the Question or
Circular Argument
• The writer defends the
claim by using the
conclusion as one of the
premises to support the
conclusion. Basically
assuming the thing to be
true that you are trying
to prove.
• Example: His lies are
evident from the
untruthful nature of his
statements.
False Delimma
• The writer only presents
some of the alternatives for
solving a problem when
more possibilities exist
because the writer assumes
that the list of alternatives
created is exhaustive.
• In the United States, one
can vote for either
Democrats or Republicans.
Guilt by Association or
Poisoning the Well
• Guilt by Association/Poisoning the Well calls
someone’s character into question by examining
the character of that person’s associates.
• Example: Sara’s friend
Amy robbed a bank;
therefore, Sara is a
delinquent. Or
Don’t listen to him
because he’s a loser.
Red Herrings
• Writers use misleading or unrelated evidence
to support a conclusion.
• Example: That painting is worthless because I
don’t recognize the artist. Or I know I forgot
to deposit the check into the bank yesterday.
But, nothing I do pleases you.
Slippery Slope
• Writers arguments
suggest that one thing
will lead to another,
oftentimes with
disastrous results.
• Example: If you get a B
in high school, you
won’t get into the
college of your choice,
and therefore will never
have a meaningful
career.