Logical Fallacies
Statistics - Basics
▪ Who
▪ Why
▪ How
▪ When
▪ Where
▪ What
Statistics - Vague Logos?
▪ Guessing?
▪ Definition(s)?
▪ Measurement(s)?
▪ Sampling?
Statistics - Vague Language
▪ “some”
▪ “many”
Statistics - MoE
▪ Sampling Error: “±N%” where N might equal 3
▪ Percentages:
▪ In September, Candidate A received 42%
▪ In September, Candidate B received 44%
▪ In August, Candidate A received 45%
▪ In August, Candidate B received 42%
▪ Polls:
▪ Sampling
▪ MoEs
▪ Comparison
Confirmation Bias
▪ When trying to determine the validity of an
assertion:
▪ Information search is highly biased towards finding
confirming evidence (gathering)
▪ Information search terminates too quickly (sampling)
Look for Common Biases
▪ I read a report in the newspaper claiming that
women are worse drivers than men. Do I believe
the report?
▪ Yes… because of my friend Carrie
▪ No… because I’m a woman and I’m a good driver
▪ Should we drill for oil in Alaska?
▪ What does *** think?
Logical Fallacies - Examples
Example . . .
…[T]he acceptance of abortion does not end with the killing
of unborn human life. It continues on to affect our attitude
toward all aspects of human life. This is most obvious in
how quickly, following the acceptance of abortion, comes
the acceptance of infanticide―the killing of babies who
after birth do not come up to someone's standard of life
worthy to be lived―and then on to euthanasia of the
aged. If human life can be taken before birth, there is no
logical reason why human life cannot be taken after birth.
▪
Source: Francis A. Schaeffer, "It is Your Life that is Involved", Who is For Life? (1984), p. 39.
Slippery Slope
Example . . .
Hate based on skin color and/or ethnic and cultural
differences still festers among us. It's an aggressive
monster that actively seeks putrefaction like itself so it
may commune and spawn. It spreads like a fungus,
seeking to multiply.
The Internet has been a fertile ground for groups to plant
evil seeds. As ways to interact on the Internet have
grown, so grow the hate groups. Online communities,
which so innocently attempt to bring like-minded
individuals together for virtual socializing, created a nice
breeding ground for venom.
Source: "Google Should Act", Contra Costa Times, 3/10/2005
Begging the Question
… or Circular Reasoning
Example . . .
…Scientology textbooks sometimes refer to psychiatry as a
"Nazi science".
Well, look at the history. Jung was an editor for the Nazi
papers during World War II. … Look at the
experimentation the Nazis did with electric shock and
drugging. Look at the drug methadone. That was
originally called Adolophine. It was named after Adolf
Hitler.
Source: "Q&A: Tom Cruise", Entertainment Weekly, 6/9/2005
False Analogy - or Guilt by Association
Example . . .
We hated the war, but we loved it too. Vietnam made us special, a
generation with a mission. Vietnam gave the semblance of moral
shape to what was actually a formless hatred of "the system." The
war justified every excess, every violent thought and deed. Heaving a
rock at some corporation's window, we banished guilt by the
thought: This is for the Vietnamese. Trying to set fire to a university
library, we said to ourselves: This is for the Vietnamese. If the war
gave us license, it also gave us an addictive sense of moral
superiority: we were better than the circumstances in which we were
forced to live. If we committed small misdemeanors of indecency,
they were in the long run justified by the much larger and more
obscene crime in Southeast Asia.
Source: Peter Collier, "Something Happened to Me Yesterday", in Destructive Generation: Second Thoughts About the
Sixties, with David Horowitz (Summit Books, 1989), p. 264.
Red Herring
Attempting to justify committing a wrong on the
grounds that someone else is guilty of another
wrong is clearly a Red Herring.
Example . . .
The case of the ecologist who linked the cycles of the Canadian lynx and its
prey, the snowshoe rabbit, with the sunspot cycle is instructive. The
ecologist analyzed records of the Hudson Bay Company, which had
been collecting pelts of the two species since 1735; he found that the
two populations fluctuated up and down, displaying a periodicity of
approximately ten years. Not surprisingly, the variations in the
predatory lynx population tended to follow the ups and downs in the
rabbit population with a time lag of a couple of years.
Then the ecologist superimposed the two curves atop a similar graph
representing the concurrent sunspot activity: voilà! The three cycles
approximately coincided over a good portion of their range. The
ecologist leaped to the conclusion that the annual fluctuations of the
lynx and rabbit populations were controlled by the eleven-year sunspot
cycle….
Source: Lawrence E. Jerome, "Astrology: Magic or Science?", in Objections to Astrology by Bart J. Bok &
Lawrence E. Jerome (Prometheus, 1975), p. 57.
Post hoc
"With this, therefore because of this" (Latin)
Example . . .
Instead of beating your chest over the current political-contribution
system, why don't you advocate a solution? The last thing our political
system needs is Time magazine sermonizing about "how the little guy
gets hurt." I'm sure there are a lot of "little guys" in the magazine
business that have been flattened by Time's fat feet too.
Source: Rob Windoffer, Chicago, "Letters", Time, February 28, 2000.
Two fallacies . . .
▪ Ad hominem
▪ Tu quoque
Example . . .
There are very few general laws of social science, but we can
offer one that has a deserved claim: the restriction of the
concept of humanity in any sphere never enhances a respect
for human life. It did not enhance the rights of slaves,
prisoners of wars, criminals, traitors, women, children, Jews,
blacks, heretics, workers, capitalists, Slavs or Gypsies. The
restriction of the concept of personhood in regard to the
fetus will not do so either.
Source: Phillip Abbott, quoted by Helen M. Alvaré in "Abortion is Immoral", from The Abortion Controversy, Greenhaven,
1995, p. 25.
Begging the question
When writers assume as evidence for their argument
the very conclusion they are attempting to prove
Example . . .
How do we know that we have here in the Bible a right
criterion of truth? We know because of the Bible's claims for
itself. All through the Scripture are found frequent
expressions such as "Thus says the Lord," "The Lord said,"
and "God spoke." Such statements occur no less than 1,904
times in the 39 books of the Old Testament.
Source: Gilbert W. Kirby, "Is the Bible True?" Decision, Vol. 1, Jan. 1974, p. 4. Cited by S. Morris Engel in Analyzing Informal
Fallacies, Prentice-Hall, 1980, p. 55.
Begging the question
Example . . .
… Quebec environment minister Lise Bacon pledged the
PCBs would be moved out and broken down somehow
within 18 months. She also said that PCBs couldn't be all
that dangerous because her father had washed his hands
in PCBs but lived to an old age.
Source: Merritt Clifton, "PCB Homecoming", Greenpeace, November/December, 1989, p. 21.
Hasty Generalization
“In understanding and characterizing general
situations, a logician cannot normally examine
every single example. However, the examples used
in inductive reasoning should be typical of the
problem or situation at hand.”
Example . . .
[The Mayor] said the biggest problem for the city
administration has been fighting people who have
protested such things as industrial development.
"We've had people fight highways, the school corporation
and county zoning," he said. "I didn't notice any of these
people coming up here on horses and donkeys. They all
drove cars up here, spewing hydrocarbons all over the
place."
Source: Terre Haute Tribune-Star
Multiple ▪ As hominem
▪ Two wrongs don’t make a right
▪ Tu quoque
Example . . .
…[H]igh-density development [doesn't] reduce congestion.
The superficially appealing idea is that if we all live closer
to where we work and shop, shorter car trips and mass
transit will replace all those long car rides. But the real
world doesn't work that way. Try this thought experiment.
What happens at a cocktail party when a new wave of
people shows up and the population density of the living
room doubles? Is it harder or easier to get to the bar and
the cheese tray? Is it harder or easier to carry on
conversation and move around the room? As urban
population density rises, auto-traffic congestion gets
worse, not better, and commute times get longer, not
shorter.
Source: Steven Hayward, "Suburban Legends", National Review, March 22, 1999, p. 36.
Weak Analogy
Example . . .
Ad in Food and Wine for American Express, showing
comedian Jerry Seinfeld with a number of
presumably new purchases--an armchair, a globe,
a laptop computer, a mountain bike, and so forth:
“A Cardmember Goes Shopping. The American
ExpressR is welcome at all kinds of places. Just ask
Jerry, who uses his Card for everyday items, as well
as for the things that make him, well, Jerry. In fact,
it’s so widely accepted, Jerry uses it wherever he
goes. No kidding.”
Appeal to Authority
Example . . .
It’s important that every family be protected by a
whole life-insurance plan. After all, what would
happen if you died? Your family would be destitute
and would probably end up on welfare.
Appeal to Fear
Example . . .
If colleges and universities continue to admit large
numbers of minorities under affirmative action,
soon there won't be any room for whites.
Multiple
▪ Genetic (racist)
▪ Slippery Slope
Example . . .
This was a commonly-heard argument after the September
11 terrorist attacks: Everybody, with one exception, in the
U.S. Congress voted to support the administration’s
decision to bomb Afghanistan after the September 11
attacks on New York’s World Trade Center and the
Pentagon. The lone dissenter was Barbara Lee, who
represents Berkeley. It’s outrageous that she had the
temerity to vote against her colleagues. She’s completely
out of step with the rest of the country, since the nation is
100% behind the bombing campaign.
Bandwagon
… and Appeal to Patriotism
Example . . .
Store advertisement: Why not join the other
discriminating shoppers and buy your china,
crystal, and silver at “Remember When”?
Appeal to Flattery
… and Snob Appeal/Bandwagon
Example . . .
When Oliver North and John Poindexter admitted
that they were committing illegal acts when they
plotted to sell arms to Iran and divert money to the
Contras during the Irangate scandal, they
defended their actions out of love for their country.
Appeal to Patriotism
Example . . .
Highway sign: “Stop in at Grandma’s Diner and relax over a
home-cooked meal. Enjoy Grandma’s famous meatloaf
and mashed potatoes in a casual, friendly atmosphere.
We’ll make you feel as if you’re right at home.”
Appeal to Tradition
Example . . .
How could an employer be so cruel as to fire a worker like
Robert Gonzalez? Of course, his absenteeism has been
significant, and he has difficulty getting to work on time.
And it’s true that customers have complained about his
rudeness. But he has seven children to support, house
payments to make, and college loans to repay.
Appeal to Sympathy
Example . . .
What was Mayor Shelton thinking of when she came up with
a plan to build a shopping center along the only open
space fronting the ocean in Princeton-by-the-Sea? Any
idiot can see that her proposal is absurd.
Ridicule
Example . . .
I’m not voting for Mayor Shelton’s idea of building a
shopping center along the only open space
fronting the ocean in Princeton-by-the-Sea! She
spends far too much money on clothes for me to
trust her with my money!
Ad hominem
Example . . .
“More than 50 dangerous pesticides contaminate Britain’s
food, official tests reveal. […] The revelation – in a survey
of official testing results – will heighten concern about
food contamination.”
Geoffrey Lean, the Independent on Sunday 27 February 2005
Multiple ▪ Appeal to Fear
▪ Out of Context
Example . . .
“Think about it: every time there’s a list of the 100 greatest
records of all time, all those albums were recorded in two
days.
Jack White, the White Stripes, Observer Music Monthly November 2004
Hasty Generalization
Example . . .
I have been a member of the NAACP for ten
years. My son cannot possibly be a bigot.
Argument from Adverse Causes
Example . . .
I guess I will receive a C on my next English
paper because the teacher said my average
was a C so far, so the chances must be that I'll
get a C on the next one.
Non sequitur
▪ It does not follow (Latin)
Friedrich Nietzche's attack on social welfare should not
be taken seriously. He is said to have been a
degenerate and it is a fact that he went insane.
You can be sure of getting the best watch possible if
you buy a Tempus Fugit watch, because you will be
buying the world's greatest watch.
Rare taste: you either have taste or you don't. (Scotch
ad)
You will get pregnant if you kiss a boy. I've seen Sally
kiss boys three times, and now she is pregnant.
My honesty is a matter of record. My enemies have tried
to bring similar charges against me before, but they
couldn't prove anything that stands up in court. That
proves I am an honest man.
Just answer the question yes or no. Were you still
selling drugs when you came to this town?
How can you justify giving this man life imprisonment by
declaring him guilty of murder? After all, since that
time he has become a devout Christian and proven to
be an exemplary prisoner during the whole time he
was on trial.
Senator Jones shouldn't be blamed for having sex with
teenage girls. After all, other senators have done
much worse things.
American citizens must raise taxes to support schools.
Without more money, our schools cannot possibly do
a good job.
The pinkos, socialistic liberals, and weirdos in that
other department are naturally against my legislative
reforms.
I interviewed the entire third floor of my dorm, and my
research shows that most of the people at this
university go home on weekends.
He is using unfair arguments because none of his
arguments are equitable. Because they are not
equitable, they are not just, and hence, unfair.
Alien abductions must take place because no one has
found any evidence to disprove the eye-witness
accounts.
We must put God back in our schools, or else American
society will degenerate.
You cannot listen to Rush Limbaugh's ideas because
he is a conservative. Conservative speaker's ideas
are not worth listening to. Since Limbaugh is
conservative, you cannot listen to his ideas.
Videos
▪ Moment
▪ Vernon Robinson for Congress