Transcript the Power Point on Logical Fallacies

CONSTRUCTING
REASONABLE
ARGUMENTS
MODES OF PERSUASION
ETHOS
• An appeal to the authority or character of the
presenter (this is where the word “ethics” comes
from)
• You can be the authority
• You can have the experience necessary
• You can “borrow” the authority through the application of
“logos”
LOGOS
• An appeal to logic or reason (this is where the word
“logic” comes from)
• You must provide evidence
• You must interpret that evidence
• You must show the sources of your evidence
• You must do this clearly
PATHOS
• An appeal to emotion (this is where the words
“sympathy” and “pathetic” come from)
• You can use a powerful analogy (like Jensen’s space aliens)
• You can use a vision of the future (like Carly Lettero’s vision
of her own death)
• But you must avoid manipulation, and you must also
employ logos.
• This works best when employed as a passionate style, rather
than as a substitute for substance.
LOGICAL FALLACIES
THE TOP TEN
HASTY GENERALIZATIONS
• These arguments are based on atypical, irrelevant, or
inaccurate evidence—usually because the sample from
which the evidence comes is too small
• “Of course our students are physically fit; just look at the
success of our sports teams!”
• “Today was colder than yesterday; climate change is a fraud!”
• “There’s no absolute agreement on climate change; therefore,
it doesn’t exist.”
• “All poets are suicidal. Look at Dorothy Parker’s poems—one of
them is all about committing suicide.”
POST HOC
(FAULTY CAUSE AND EFFECT)
• These arguments are based on the assumption that if
event B happens after event A, then event B must be
caused by event A.
• “Tourism in this city started to decline right after Mayor Scott
was elected. To save our tourist industry, let's replace her now!”
• “The Climate started to warm after the Industrial Revolution
began. Therefore, Climate Change is caused by the Industrial
Revolution.”
• “Margtaret Atwood wrote much of her poetry after Duncan
Campbell Scott; therefore, her poetry must be influenced by
his.”
REDUCTIVE REASONING
• This is an attempt to explain a complex effect through a
simple cause (oversimplification).
• “My aunt lived to be ninety-four. She drank a glass of beer
every day. If we all drink a glass of beer every day, we will live
to be ninety-four.”
• “Wind turbines use no fossil fuels to produce energy. Therefore,
we can avoid Peak Oil by switching to wind energy.”
• “Ambrose Bierce wrote a story that was sympathetic to a
slave-holding plantation-owner. He must have approved of
slavery.”
FALSE ANALOGIES
• This occurs when a writer tries to draw similarities
between two things that are so dissimilar that the
comparison is absurd.
• “Why do I have to take English in order to graduate? I don’t
have to buy vegetables to leave the grocery store!”
BEGGING THE QUESTION
• This one is frequently misinterpreted. What it means
is to assume that the point you are arguing is true. If
this really were the case, the point would not need
arguing. This should not be confused with the
attempt to argue something that is incontrovertible.
• “Improving public transportation in this city won't solve
highway congestion. Even if public transportation is clean,
safe, and efficient, people will still prefer to use their cars.”
• “In tragedies, people die at the end of the story. The Taming
of the Shrew is not a tragedy because no one dies at the
end.”
CIRCULAR REASONING
• The argument consists of stating the conclusion it
was meant to support.
• “The priest is a good person because he is virtuous.”
• “If the story had a different plot, the ending would be
different.”
AD HOMINEM
• This means attacking the person rather than the
argument (and was used extensively against Bill Clinton
after the Monica Lewinsky scandal).
• “We can’t trust Bill Clinton to lead the country; he had an affair
with an intern.”
• “None of Al Purdy’s poetry is any good; he was an alcoholic.”
• a similar fallacy is the “straw man,” where a position is
presented in its most extreme form in order to discredit its
proponents.
FALSE DILEMMA/DICHOTOMTY
• This comes from the assumption that there are only a
very limited number (usually two) of interpretations or
truths.
• “Either 1+1=4 or 1+1=5. 1+1 does not equal 4; therefore, 1+1=5.”
• “Either we support the death penalty or we allow crime to run
rampant.”
• “Either we continue with the economy of growth, or we go
back to living in caves.”
• “Either you’re with us, or you’re against us.”
APPEAL TO POPULARITY
• This is the “everybody’s doing it, we should too” or
“everybody thinks so” argument. I don’t think we need
examples here!
• Closely related, though, is the appeal to history: because
things have always happened this way, they will
continue to happen the same way. This is also a form of
“post-hoc” argument. Here’s the best (and most
frightening) example:
“We’ve always been able to use technology to solve our
problems before; therefore, we’ll be able to
technologically innovate our way out of Climate Change
and Peak Oil as well.”
NON SEQUITURS
• Literally, this means “it does not follow.” It happens
when there really isn’t a clear connection between
the premise (or starting point of the argument) and
the conclusion
• “Maria loves college, so she will make a great teacher.”
• “Shakespeare wrote lots of great poems, so this poem by
Shakespeare must be great.”
OTHER FALLACIES TO AVOID:
• Appeal to Authority: Just because Dr. Smartypants
says it’s true doesn’t mean it is. Make your own
argument!
• Appeal to Common Practice: aka “the lemming
argument.” If everyone jumped off a bridge, would
you do it too?
• Appeal to Novelty: New is not better; it’s just new.
Likewise length; likewise moderate positions.
• Appeal to Composition: individuals in a group have
characteristics a, b, and c; therefore, the group
must have characteristics a, b, and c. (This one
leads to –and explains—a great deal of prejudice).
THINGS TO REMEMBER
• Most of the conclusions included in the examples
above could be argued. The problem is that the
reasoning provided in these examples is insufficient
or not credible.
• The best way to "smoke out" unsound reasoning in
your own writing is to ask yourself what your
argument takes for granted. Remove those
assumptions, then rebuild your argument using
stronger support--if such support exists.