Transcript Logical Fallacies

Logical Fallacies
What is a logical fallacy?
A logical fallacy is an error in logic that can make a
plausible, but misleading argument.
Inductive fallacies:
Inductive fallacies are the result of the incorrect use of evidence.
Ex: “This chalk is white; therefore, all chalk is white.”
*With inductive fallacies, an arguer leaps to a conclusion based on insufficient
evidence*
Deductive fallacies:
Deductive fallacies are the result of a failure to follow the logic of a series of
statements.
Ex: “The rooster crows at 5:00 AM, and the sun rises at 5:00 AM; therefore the
rooster makes the sun rise.”
*With deductive fallacies, an arguer makes an incorrect or unsupported link
between cause and effect*
Logical Fallacies (cont.)
While there are two main categories of logical
fallacies, it is important to note that there is
often overlap.
Some fallacies may fit into both categories.
However, it is important to note that logical fallacies occur when :
a)An arguer incorrectly links cause and effect.
b)An arguer leaps to a conclusion based on insufficient evidence.
#1.) HASTY GENERALIZATION:
Prematurely jumping to a presumptuous conclusion.
Prejudices and superstitions are the result of making a hasty generalization.
Ex: “There was a news story about a guy in a fraternity who was a rapist, so
now I carry mace if I know I’ll be going anywhere near a frat house.”
How is this an example of the Hasty Generalization logical fallacy?
It’s a prejudiced point of view. The arguer assumes that because one person
in a fraternity is a rapist, all people in fraternities are rapist. The arguer is
jumping to a presumptuous conclusion about people in fraternities.
#2.) FALSE AUTHORITY:
Falsely recognizing someone as an authority on something.
Accepting someone’s credentials without careful evaluation.
EX:
http://www.youtube.com/watch?v=bZIzRqDOSZo
How is this commerical an example of the Faulty Use of Authority logical
fallacy?
Each commercial assumes a connection between the specific celebrity’s
popularity and their authority on the product or service they are
promoting.
#3.) POST HOC/FALSE CAUSE
Post Hoc, Ergo Propter Hoc: “after this, therefore because of this.”
Assuming that because one event follows another, the first event is the
cause of the second.
Ex: “The rooster crows at 5:00 AM, and the sun rises at 5:00 AM; therefore
the rooster makes the sun rise.”
How is this an example of the Post Hoc logical fallacy?
The arguer assumes that simply because these two events occur sequentially,
there is a cause and effect relationship between them.
Ex: “A tornado hit my town after a group of Satan worshippers moved in, so
god sent the tornado to punish us for allowing them to move here.”
How is this an example of the Post Hoc logical fallacy?
The arguer assumes a connection between the Satan worshippers and the
tornado.
Post Hoc- Correlation vs Causation
• Just because two things are related
(correlated) doesn’t mean that one caused the
other.
• For example– the murder rate has decreased,
while the average temperature has increased
steadily since 1975. Therefore, global warming
prevents murder.
Post Hoc- Correlation vs. Causation
Post Hoc- Magical Thinking
• “Last time I walked past a black cat, I tripped
and hurt my arm, so now it must have been
the cat.”
• Mr. Governor issues a proclamation for the
people of his state to pray for rain. Several
months later, it rains. Praise the gods!
• I knew I should have helped that old lady
across the road. Because I didn’t, I have been
having bad Karma all day.
#4.) FALSE ANALOGY:
Drawing an analogy or comparison between two situations that are totally
dissimilar.
Ex: “We know that overweight people have a higher mortality rate than thin
people. We also know that black people have a higher mortality rate than
white people. Do we subject black people to torturous treatments to bleach
their skin? Of course not. We have enough sense to know that skin-bleaching
will not eliminate sickle-cell anemia. So why do we have blind faith that
weight loss will cure the diseases associated with obesity?”
-Susan Wooley, Director of eating disorders clinic at The University of
Cincinnati.
How is this an example of the False Analogy logical fallacy?
The arguer assumes that skin color and weight are analogous. She assumes that
diseases that are specific to people of a certain skin color can be treated just
like diseases that are specific to people of a certain weight.
#5.) AD HOMINEM:
Attacking a person’s character rather than their statements.
Latin for “against the man.”
Ex: “Ernest Hemingway was an alcoholic and a terrible father, so I won’t read
his books.”
How is this an example of the Ad Hominem logical fallacy?
The arguer is attacking Ernest Hemingway’s character rather than his
intellectual output.
Ex: "She asserts that we need more military spending, but that is false, since
she is only saying it because she is a Republican."
A person's interests and circumstances have no bearing on the truth or falsity
of the claim being made. While a person's interests will provide them with
motives to support certain claims, the claims stand or fall on their own.
#6.) FALSE DILEMMA:
Poses an “either/or” situation by suggesting that only two options are
possible.
*Sometimes called the “black/white” fallacy*
Ex: “If you don’t watch football, you’re not a real man.”
How is this an example of the False Dilemma logical fallacy?
This statement poses an “either/or” scenario in which a person either
watches football (therefore making them a “real man”) or that person
does not watch football (in which case they are not a “real man”).
#6.) FALSE DILEMMA (Cont.):
Ex:
“Trust fund babies and corporate weasels are not allowed to read this
book…if you are in one of these categories, here’s my first piece of advice:
you must learn to be a problem solver not a problem creator.”
-Bill O’Reilly, Who’s Looking Out For You?
How is this an example of the False Dilemma logical fallacy?
Bill O’Reilly poses a situation in which one is either a “problem solver” or a
“problem creator” without evaluating any middle ground in between the
two.
#7.) SLIPPERY SLOPE:
Claiming that one event will trigger a series of similar, undesirable events.
*If an arguer fails to provide evidence to support his or her claim that one
event will lead to a similar, undesirable event, then they are guilty of the
“slippery slope” fallacy.
Ex:
“Cloning animals should be illegal because that would lead to cloning
humans, and then we would have a race of clones.”
How is this an example of the slippery slope logical fallacy?
The arguer assumes that if cloning of animals is allowed, then cloning of
humans will be too. Then, the arguer assumes that this hypothetical
cloning of humans will grow out of control.
#7.) SLIPPERY SLOPE (Cont):
Ex:
“If they legalize gay marriage, then they will legalize bestiality and
pedophilia.”
How is this an example of the Slippery Slope logical fallacy?
The arguer jumps to the conclusion that if gay marriage is legalized, then
other undesirable things will also be legalized.
#8.) BEGGING THE
QUESTION/CIRCULAR LOGIC
A circular argument. When an arguer makes a statement that assumes that
the very question being argued is already answered. The premises
assume that the conclusion is true.
Ex: “Women should not be permitted into the men’s club because the club is
only for men.”
How is this an example of the Begging the Question logical fallacy?
The arguer does not adequately answer the original question (“why
shouldn’t women be permitted into men’s clubs?”). Instead, the arguer
treats the question as if it has already been answered.
• Ex: Paranormal activity is real because I have experienced what can only
be described as paranormal activity.
• EX: If such actions were not illegal, then they would not be prohibited by
the law.
#9.) STRAW MAN:
Setting up an extreme example of an opposing view to argue against.
Ex:
“Listen, you trust-fund babies and children of privilege, if you’re going to drink
a quart of bourbon every day and smoke crack, this book is not for you.”
-Bill O’Reilly, Who’s Looking Out For You?
How is this an example of the Straw Man logical fallacy?
Bill O’Reilly sets up an extreme example of “trust-fund babies” and
“corporate weasels.” His example is so extreme that it becomes very easy
to argue against.
Ex: "Senator Jones says that we should not fund the attack submarine
program. I disagree entirely. I can't understand why he wants to leave us
defenseless like that."
Attacking a distorted version of a position simply does not constitute an
attack on the position itself.
#10.) Tu Quoque:
A rebuttal to an argument which does not refute the allegations, but simply
counterattacks.
Ex:
“My step dad says I’m irresponsible, but I’m not. Besides, he’s a jerk.”
How is this an example of the Tu Quoque fallacy?
The arguer does not refute the allegations that they are irresponsible;
instead, they simply counterattack.
Ex:
• Helga: You should not be eating that... it has been scientifically proven
that eating fat burgers are no good for your health.
• Hugh: You eat fat burgers all the time so that can’t be true.
It doesn’t matter (to the truth claim of the argument at least) if Helga follows
her own advice or not.
# 11.) NON-SEQUITUR:
A totally illogical connection between cause and effect.
Ex. People generally like to walk on the beach. Beaches have
sand. Therefore, having sand floors in homes would be a great idea!
As cool as the idea of sand floors might sound, the conclusion does not follow
from the premises. The fact that people generally like to walk on sand
does not mean that they want sand in their homes, just like because
people generally like to swim, they shouldn’t flood their houses.
Ex. Buddy Burger has the greatest food in town. Buddy Burger was voted #1
by the local paper. Therefore, Phil, the owner of Buddy Burger, should run for
President of the United States.
• I bet Phil makes one heck of a burger, but it does not follow that he should
be President.
#12.) AD POPULUM/BANDWAGON:
When an arguer assumes that he or she can neglect properly supporting his
or her argument by appealing to a thread of commonly held beliefs
Ex: “If leprechauns aren’t real, then why do so many people believe in them?”
No amount of believing in them will make leprechauns real.
Ex: “Ten million (and counting) Americans can't be wrong, can they?“
Ten million Americans can be wrong, though.
#13) Equivocation
• When a key term or phrase in an argument is used
in an ambiguous way, with one meaning in one
portion of the argument and then another meaning
in another portion of the argument.
• EX: A warm beer is better than a cold beer. After all,
nothing is better than a cold beer, and a warm beer
is better than nothing.
We used two meanings of the word “nothing
interchangeably.
Equivocation (continued)
• EX: I have the right to watch "The Real
World." Therefore it's right for me to watch
the show. So, I think I'll watch this "Real
World" marathon tonight instead of studying
for my exam.
• EX: Noisy children are a real headache. Two
aspirin will make a headache go away.
Therefore, two aspirin will make noisy children
go away.
#14) Middle Ground
• Assumes that the middle position between
two extremes must be correct simply
because it is the middle position. This sort of
"reasoning" has the following form:
• Position A and B are two extreme positions.
• C is a position that rests in the middle between
A and B.
• Therefore C is the correct position.
Middle Ground (continued)
• Example: Congressman Jones has proposed
cutting welfare payments by 50% while
Congresswoman Shender has proposed
increasing welfare payments by 10% to keep
up with inflation and cost of living increases. I
think that the best proposal is the one made
by Congressman Bumple. He says that a 30%
decrease in welfare payments is a good
middle ground, so I think that is what we
should support.
#15) Moving the Goalposts
• Demanding from an opponent that he or she
address more and more points after the initial
counter-argument has been satisfied refusing to
conceded or accept the opponent’s argument.
Example:
The moon landing were a hoax because we have no
photos of the sites.
Okay, we now have photos of the sites, but those are
clearly photoshopped.
#16) No True Scotsman
• When a universal (“all”, “every”, etc.) claim is
refuted, rather than conceding the point or
meaningfully revising the claim, the claim is altered
by going from universal to specific, and failing to
give any objective criteria for the specificity.
Logical Form:
• All X are Y.
• (it is clearly refuted that all X are not Y)
• Then all true X are Y.
No True Scotsman (continued)
• Example :
• John: Members of the UbaTuba White Men's Club are
upstanding citizens of the community.
• Marvin: Then why are there so many of these members in
jail?
• John: They were never true UbaTuba White Men's Club
members.
• Marvin: What’s a true UbaTuba White Men's Club member?
• John: Those who don't go to jail.
No True Scotsman (continued)
• "Real men eat meat“
• "Real Americans don't question the existence of
God"
• "Real artists don't use a computer“
• Angus declares that Scotsmen do not put sugar on
their porridge, to which Lachlan points out that he is
a Scotsman and puts sugar on his porridge. Furious,
like a true Scot, Angus yells that no true Scotsman
sugars his porridge.
#17) Appeal to Tradition
Assumes 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:
• X is old or traditional
• Therefore X is correct or better.
• EX: 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.
#18) Biased Sample
• When a person draws a conclusion about a
population based on a sample that is biased or
prejudiced in some manner.
• EX: Large scale polls were taken in Florida, California,
and Maine and it was found that an average of 55%
of those polled spent at least fourteen days a year
near the ocean. So, it can be safely concluded that
55% of all Americans spend at least fourteen days
near the ocean each year.
#19) Cherry Picking
• When only select evidence is presented in
order to persuade the audience to accept a
position, and evidence that would go against
the position is withheld.
• EX: My political candidate gives 10% of his
income to the needy, goes to church every
Sunday, and volunteers one day a week at a
homeless shelter. Therefore, he is honest and
morally straight.
#20) Appeal to Ignorance
• The burden of proof is placed on the wrong side, or a lack of
evidence for side A is taken to be evidence for side B in cases
in which the burden of proof actually rests on side B.
EX:
• Bill: "I think that some people have psychic powers."
Jill: "What is your proof?"
Bill: "No one has been able to prove that people do not have
psychic powers."
• The absence of evidence does not constitute evidence.
Appeal to Ignorance (continued)
•
•
•
•
John: Unicorns exist.
Jane: Can you prove that unicorns exist?
John: Can you prove that they don’t?
The burden of proof is not on Jane to prove that
unicorns don’t exist. John has made a claim and it is
his job to back up his claim.
• Note: The burden of proof is the obligation to prove
one’s assertion. The burden of proof belongs to the
side making a claim.
#21) Loaded Language
• Substituting facts and evidence with words
that stir up emotion, with the attempt to
manipulate others into accepting the truth of
the argument.
• The phrase “family values“ immediately
invokes the feelings of warmth, security,
honesty and support that a family brings, even
though the term really means a few pet social
issues - hatred of gays, being anti-abortion,
and restricting roles for women.
Loaded Language (continued)
• “Insurgent,” “freedom fighter,” and “terrorist”
can all be applied to the same group
depending on the speaker's perspective.
• The "USA PATRIOT Act" is a (brutally forced)
acronym for Uniting and Strengthening
America by Providing Appropriate Tools
Required to Intercept and Obstruct Terrorism
Act, but due to the title, it implies that those
opposed to the Act are inherently unpatriotic.
#22) Erroneous Appeal to Emotion
• This is the general category of many fallacies
that use emotion in place of reason in order
to attempt to win the argument. It is a type
of manipulation used in place of valid logic.
• Emotions manipulated can include pity, fear,
flattery, and others.
• Appealing to emotion is a necessary rhetorical
strategy (think pathos), but is not a substitute
for logical thinking.
Erroneous Appeal to Emotion
(continued)
• Ex. Power lines cause cancer. I met a little boy
with cancer who lived just 20 miles from a
power line who looked into my eyes and said,
in his weak voice, “Please do whatever you
can so that other kids won’t have to go
through what I am going through.” I urge you
to vote for this bill to tear down all power
lines and replace them with monkeys on
treadmills.