Logical Fallacies
What is a Fallacy?
A fallacy is an error in reasoning or a flawed
argument.
A fallacy is an "argument" in which the
premises (reasons) given for the conclusion
do not provide the needed degree of support.
Fallacies may be created unintentionally, or
they may be created intentionally in order to
deceive other people.
Prevalence of Fallacies
Fallacies are all around you…
Advertisements in magazines, on T.V., on
billboards all contain fallacies.
Politicians use fallacies to persuade you.
Types
of
Fallacies
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Ad Hominem (Personal Attack)
Appeal to Tradition
False Analogy
False Authority
False Cause (Post Hoc)
False Dilemma (Either/Or Fallacy)
Hasty Generalization
Appeal to Fear
Slippery Slope
Straw Man
Ad Hominem or Personal Attack
Ad Hominem (“against the person”) attacks a
person’s character and not the person’s issue
or reasoning.
The major difficulty with labeling a piece of
reasoning as an ad hominem fallacy is deciding
whether the personal attack is relevant.
Example: Why should we think a candidate
who recently divorced will keep her campaign
promises?
Appeal to Tradition
Occurs when it is assumed that something is better or
correct simply because it is older, traditional, or "always
has been done." This sort of "reasoning" has the following
form:
1. X is old or traditional
2. Therefore X is correct or better.
Example: Of course this mode of government is the
best. We have had this government for over 200 years
and no one has talked about changing it in all that time.
So, it has got to be good.
False Analogy
An inaccurate, inappropriate, or misleading
comparison between two things.
Example: What's the big deal about the early
pioneers killing a few Indians in order to
settle the West? After all, you can't make an
omelet without breaking a few eggs.
False Authority
When the person in question is not a
legitimate authority on the subject. The most
blatant examples of misplaced appeals to
authority appear in advertising “testimonials.”
Example: We are urged to drive an
automobile of a given make because a
famous golfer or tennis player affirms its
superiority.
False Cause
False Cause (or Post Hoc) - a fallacy with the
following form:
1. A occurs before B.
2. Therefore A is the cause of B.
False Cause wrongly assumes a cause and effect
relationship.
Example: A year after the release of the violent shoot’em-up video game Annihilator, incidents of school
violence tripled—surely not a coincidence.
Example: It’s Friday the 13th. Mistakes happen on this
day!
False Dilemma or Either/Or
Reduces complicated issues to only two
possible courses of action.
Example: The patent office can either
approve my generator design immediately
or say goodbye forever to affordable
energy.
Hasty Generalization
Draws conclusions from scanty evidence.
Example: I wouldn’t eat at that restaurant.
When I ate there once, my entree was
undercooked.
Example: I’ve met two people in Nicaragua
so far, and they were both nice to me. So,
all people I will meet in Nicaragua will be
nice to me.
Appeal to Fear or Scare Tactics
An attempt to frighten people into agreeing with
the arguer by threatening them or predicting
unrealistically dire consequences.
Example: "You know, Professor Smith, I really
need to get an A in this class. I'd like to stop by
during your office hours later to discuss my
grade. I'll be in your building anyways, visiting
my father. He's your dean, by the way. I'll see
you later."
Slippery Slope
Suggests that one thing will lead to another,
often times 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.
Straw Man
Oversimplifies an opponent's viewpoint and
then attacks that hollow argument.
Example: People who don't support the
proposed state minimum wage increase
hate the poor.
Bill and Jill are arguing about cleaning out their
closets:
Jill: "We should clean out the closets. They are
getting a bit messy."
Bill: "Why? We just went through those closets
three months ago.”
Jill: “You just want to keep all your junk forever,
which is just ridiculous."
Identify the fallacy:
1. A husband comforts his wife. The wife is near tears.
Husband: Stop worrying. Please…calm down!
Wife: You just don't understand! She's only 13. If she
goes to the movies with a boy this weekend, she'll be
married in four years; she'll never go to college. She'll
be driving kids to kindergarten before she's 20!
a. False dilemma - either/or
b. Straw man
c. Slippery slope
Identify the fallacy:
2. One guy sits eating. His friend walks in limping.
GUY: (to limping friend) What happened to you?
FRIEND: I just twisted my ankle on the curb!
GUY: I knew it! You walked under that ladder this
morning. Bad luck! Here! throw some salt over your
shoulder!
a. Ad hominem (attacking the person)
b. Hasty generalization
c. Post hoc..(false cause)
Identify the fallacy:
3. Businessman speaks on the phone.
BUSINESSMAN: The English in this application letter
is terrible. Citizens should stop providing tax money to
the state college if it graduates students like this!
a. False authority
b. Hasty generalization
c. Ad hominem
Identify the fallacy:
4. Two friends getting coffee during a break.
QUESTIONER: So! Who is your choice for Mayor?
FRIEND: I would never vote for Jones!
QUESTIONER: Why?
FRIEND: He has a big car, a big house. He's probably a
rich snob; he won't understand the average guy.
a. False cause
b. False analogy
c. Ad hominem (attacking the person)
LOGICAL FALLACIES PRACTICE
• INSTRUCTIONS:
• In groups, explain a scenario in which
each of the 10 logical fallacies may be
used. Then, a group member will present
a scenario to the class to see if they can
identify which one is being used.