Transcript Informal Logic, Famous Fallacies

Don’t Be Fooled by Bad Arguments
Distinguish arguments from
explanations:
Arguments are the assertion of a
conclusion from reasons that
are better known than the
conclusion.
Explanations are the assertion of
reasons for a conclusion that is
better known than those
reasons.
Argumentum ad Hominem (Argument to the Person): Attacking the
arguer instead of their argument.
Famous response to an ad hominem attack:
“I may be the devil’s brother, sir,
but you still haven’t answered my argument.”
3 Kinds of ad Hominem arguments:
Abusive ad Hominem:
“I believe murderers should die for the sake of their victim’s family.”
“Only a total jerk would want anyone to die!”
…does the speaker being a jerk have anything to do with whether capital
punishment is justified based on concern for the victim’s family?
Circumstantial ad Hominem:
“I believe murderers should die for the sake of the
victim’s family.”
“Well, since your cousin was murdered, it isn’t hard to
see why you feel that way.”
Tu Quoque (you too):
“I believe murderers should die for the sake of the
victim’s family.”
“Well, I recall you defending your Uncle when he was
convicted … you weren’t suggesting he die for the
family of the guy he shot!”
Appeal to Ignorance (ad Ignorantiam):
Arguing from a lack of knowledge:
No one has proven X true, (or false)
X is false (or true)
“God does not exist.”
“Says who?”
“Well, no one has proven God exists, so he doesn’t.”
“God exists.”
“Says who?”
“Well, no one as proven God doesn’t exist, so he does.”
Exceptions (below are good arguments (pretty
good)):
“Guy’s innocent.”
“Says who?”
“Well, he hasn’t been proven guilty, so he is
innocent.”
“There is no crocodile in the hall.”
“Says who?”
“Well, no one has proven there’s a crocodile in the
hall, so there isn’t.”
Appeal to the Majority:
The fallacy has the form:
X is popular
X is true
Direct Approach: appeal directly to the crowd of
people … use emotive language to create mob
mentality support for a conclusion. Political
speeches often good examples?
Indirect Approach: appeal indirectly to the crowd by
appealing directly to individuals and their
relationship to the crowd … also called a
“Bandwagon Argument”:
“Come on … everyone in this class smokes crack ... you
should take a hit!”
Individual
crowd
Appeal to the People (Argumentum ad Populum):
Ad Populum has the form:
X is popular
X is true
When the majority’s opinion becomes enshrined over
time it becomes a tradition. Think of Appeal to
Tradition as an instance of Indirect Appeal to the
Majority
If your school had a tradition of crack smoking, the
example below would be appeal to tradition.
“Come on … everyone in this class smokes crack ... you
should take a hit!”
Individual
crowd
Appeal to Force or Fear:
Supporting or avoiding a conclusion by threats
Worst case:
when debates get derailed by jeering or “shouting
down” an arguer so that the argument can’t be
heard.
More subtle case:
“I think we should choose xBox over Playstation
because its online multiplayer stuff is better.”
“How about I stomp your guts out? How would that
be?”
Committing Appeal to Fear is less an error in
reasoning, more a bullying tactic. Either way, the
response is irrelevant to the quality of the
argument.
Appeal to Pity (Argumentum ad
Misericordiam):
“I’m afraid going 70 in a 25mph zone
means you deserve this ticket, Ms.
Garcia.”
“No, Judge, I have three kids, late bills,
and work two jobs … I can’t deserve
this speeding ticket!”
Is the sorry state of the arguer logically
relevant to deserving the ticket?
Might the judge considering it in
sentencing?
Absolutizing Rules
(Misapplying a Rule)
“Yes I told the axe
murderer where the
little girl was! … if you
check your bible, you’ll
find Thou Shalt Not Lie”
To have a double standard is to apply two
different rules or judgments to one and the
same thing or kind of thing.
What a jerk! She totally shouldn’t be sitting
with that guy when she has a boyfriend!
Yeah, but you sit with Betty sometimes and you
have a girlfriend!
Yeah, but that’s different. I’m a guy!
Notice the relationship with Tu Quoque, the “You
too!” fallacy:
1.
Having a double standard doesn’t make the
claim “she’s a jerk” false. It still might be true. It
simply means that if it’s true, “he’s a jerk” is true
as well.
2. On the flip side, perhaps it’s false that “she’s a
jerk” for sitting with a boy. It will follow that
“he’s a jerk” for sitting with a girl is false.
False Bifurcation:
▪
▪
▪
▪
▪
False Dichotomy
Faulty Dilemma
Black and White Thinking
Either/Or fallacy
False Choice
Either ice cream or tantrum … you
choose! (from kid)
Either exercise or heart attack …
you choose! (from Doc)
*Ultimatums are rarely False
Bifurcations, but can be
Note how premises are red, just like the conclusions. Bifurcation is a
fallacy of presumption.
With multiplication, 12 is either 6x2 or 4x3 … so, which is it, kid?
When cooking chicken, it’s either frying or baking. So, what do you
want to do?
Note also there are many genuine bifurcations, trifurcations,
tetrafurcations, etc.:
Either the universe was created by an intelligent being or it is eternal
or it had a natural origin.
It’s either chocolate or vanilla … that’s all we have.
Missing the Point:
“So, you say Bill punched Bob in the nose? All
right, better get Bob straight to the emergency
room!”
Sometimes MtP is jumping to a distant conclusion.
Sometimes MtP is just missing the point.
“That’s a priceless Steinway! Not anymore.”
“If you’re not out of here … in 5 seconds! ...
Ah, I could easily be out of here in three!”
Hasty Generalization (Converse Accident):
Taking a small sample, and inferring from it all or
most of that kind are the same.
“My cabbie in New York City was surly, so, all
cabbies in NYC are surly.”
Exceptions:
1.
“This Root Beer, Roundy’s, is blah, so all
Roundy’s Root Beer is blah.”
2. “This Pit Bull (Rottweiler, Tarantula, Python,
etc.) is dangerous, so, all Pit Bulls (Rottweilers,
Tarantulas, Pythons, etc.) are dangerous.”
Two more things regarding the logic of danger (#2):
1.
When people say Pit Bulls, for instance, are dangerous, they plainly don’t
mean to include dead ones, very old ones, very young ones. Their statement
is perhaps elliptical for, “these healthy adult dogs can kill you and animals
are unpredictable. Be on guard!” You must decide if a statement is straightforward or elliptical based on context, knowledge of the speaker, or by
asking, if possible.
1.
Risk assessment logic: Risk assessments have 2 parts:
▪
▪
probability and,
severity.
Some things have very low probabilities of harm, but are dangerous because of
high severity. Commonly believed dangerous things:
▪
▪
▪
▪
▪
your weird looking neighbor,
flying in a commercial jet,
driving a car without a seatbelt,
playing just one round of Russian Roulette,
hitchhiking.
All have very low probabilities of harm. How then are they dangerous?
We should give that new
position to Frank
Thompson. Frank has six
hungry kids to feed, and
his wife needs an
operation to save her
eyesight.
aH = ad Hominem
AF = Appeal to Feelings
Ape = Appeal to the Majority / T
AI = Appeal to Ignorance
Ab = Absolutizing Rules
DS = Double Standard
FB = False Bifurcation
HJ = Hasty Judgment
NF = No Fallacy
Professor Pearson’s
arguments in favor of the
theory of evolution
should be discounted.
Pearson is a cocainesnorting sex pervert and,
according to some
reports, a member of the
communist party.
aH = ad Hominem
AF = Appeal to Feelings
Ape = Appeal to the Majority / T
AI = Appeal to Ignorance
Ab = Absolutizing Rules
DS = Double Standard
FB = False Bifurcation
HJ = Hasty Judgment
NF = No Fallacy
Some of you oppose the
appointment of David Cole
as new sales manager. Upon
further consideration, I am
sure you will find him
suitable for the job. If not
confirmed, it may be
necessary to make severe
personnel cutbacks in your
department.
aH = ad Hominem
AF = Appeal to Feelings
Ape = Appeal to the Majority / T
AI = Appeal to Ignorance
Ab = Absolutizing Rules
DS = Double Standard
FB = False Bifurcation
HJ = Hasty Judgment
NF = No Fallacy
You should read Irving
Stone’s latest novel right
away. It has sold over a
million copies, and
nearly everyone in the
Manhattan cocktail
circuit is talking about it.
aH = ad Hominem
AF = Appeal to Feelings
Ape = Appeal to the Majority / T
AI = Appeal to Ignorance
Ab = Absolutizing Rules
DS = Double Standard
FB = False Bifurcation
HJ = Hasty Judgment
NF = No Fallacy
Actress Andie MacDowell
says that it’s healthy to
drink milk. But the dairy
industry pays MacDowell
thousands of dollars to
make these ads.
Therefore, we shouldn’t
take her testimonials too
seriously.
aH = ad Hominem
AF = Appeal to Feelings
Ape = Appeal to the Majority / T
AI = Appeal to Ignorance
Ab = Absolutizing Rules
DS = Double Standard
FB = False Bifurcation
HJ = Hasty Judgment
NF = No Fallacy
Dr. Morrison has argued that
smoking is responsible for the
majority of health problems in
this country and that every
smoker concerned about his or
her health should quit.
Unfortunately, however, we must
consign Dr. Morrison’s argument
to the trash bin. Only yesterday I
saw none other than Dr. Morrison
himself smoking a cigar.
aH = ad Hominem
AF = Appeal to Feelings
Ape = Appeal to the Majority / T
AI = Appeal to Ignorance
Ab = Absolutizing Rules
DS = Double Standard
FB = False Bifurcation
HJ = Hasty Judgment
NF = No Fallacy
If you give Jane a cookie, she’ll want a glass of milk.
Then, she won’t be hungry for her supper!
aH = ad Hominem
AF = Appeal to Feelings
Ape = Appeal to the Majority / T
AI = Appeal to Ignorance
Ab = Absolutizing Rules
DS = Double Standard
FB = False Bifurcation
HJ = Hasty Judgment
NF = No Fallacy
Ellen is a mean drunk. I wouldn’t invite her to your
kegger, if I were you.
aH = ad Hominem
AF = Appeal to Feelings
Ape = Appeal to the Majority / T
AI = Appeal to Ignorance
Ab = Absolutizing Rules
DS = Double Standard
FB = False Bifurcation
HJ = Hasty Judgment
NF = No Fallacy
Probably no life exists on Venus. Teams of scientists
have conducted exhaustive studies on the planet’s
surface and atmosphere, and no living organisms
have been found.
aH = ad Hominem
AF = Appeal to Feelings
Ape = Appeal to the Majority / T
AI = Appeal to Ignorance
Ab = Absolutizing Rules
DS = Double Standard
FB = False Bifurcation
HJ = Hasty Judgment
NF = No Fallacy