Transcript Logical-Fallacies

LOGIC VOCAB
• Premise: Proposition used as evidence in an argument.
• Conclusion: Logical result of the relationship between the
premises. Conclusions serve as the thesis of the argument.
• Argument: The assertion of a conclusion based on logical
premises.
• Syllogism: The simplest sequence of logical premises and
conclusions, devised by Aristotle.
• Enthymeme: A shortened syllogism which omits the first premise,
allowing the audience to fill it in. For example, "Socrates is mortal
because he is a human" is an enthymeme which leaves out the
premise "All humans are mortal."
• Induction: A process through which the premises provide some
basis for the conclusion.
• Deduction: A process through which the premises provide
conclusive proof for the conclusion.
DOES LOGIC
ALWAYS WORK?
• Logic is a very effective tool for persuading an
audience about the accuracy of an argument.
However, people are not always persuaded by logic.
Sometimes audiences are not persuaded because
they have used values or emotions instead of logic to
reach conclusions. But just as often, audiences have
reached a different logical conclusion by using
different premises. Therefore, arguments must often
spend as much time convincing audiences of the
legitimacy of the premises as the legitimacy of the
conclusions.
So how do I find fallacies in my
own writing?
• Here are some general tips for finding fallacies in your
own arguments:
• Pretend you disagree with the conclusion you’re
defending. What parts of the argument would now
seem fishy to you? What parts would seem easiest to
attack? Give special attention to strengthening those
parts.
• List your main points; under each one, list the
evidence you have for it. Seeing your claims and
evidence laid out this way may make you realize that you
have no good evidence for a particular claim, or it may
help you look more critically at the evidence you’re
using.
So how do I find fallacies in my own writing?
• Learn which types of fallacies you’re especially prone
to, and be careful to check for them in your work. Some writers
make lots of appeals to authority; others are more likely to rely on
weak analogies or set up straw men. Read over some of your old
papers to see if there’s a particular kind of fallacy you need to
watch out for.
• Be aware that broad claims need more proof than
narrow ones. Claims that use sweeping words like “all,” “no,”
“none,” “every,” “always,” “never,” “no one,” and “everyone” are
sometimes appropriate—but they require a lot more proof than lesssweeping claims that use words like “some,” “many,” “few,”
“sometimes,” “usually,” and so forth.
• Double check your characterizations of others,
especially your opponents, to be sure they are accurate and fair.
Rhetorical Appeals
o Ethos, Pathos, and most importantly Logos
• Ethos - ethics or ethical. Better known as
“image”
• Pathos - the emotion of the audience
• Logos – logic of the argument.
▫ Persuasion, to a large extent, involves convincing people to accept our
assumptions as probably true. Similarly, exposing questionable assumptions
in someone else's argument is an effective means for preparing the audience
to accept your own contrary position
Example: Pointing to a fancy chart, Roger shows
how temperatures have been rising over the past
few centuries, whilst at the same time the
numbers of pirates have been decreasing; thus
pirates cool the world and global warming is a
hoax.
a. slippery slope
b. black-or-white
c. bandwagon
d. false cause
Example: The fallacy of urging an audience to
“root for the underdog” regardless of the issues
at hand. “Those poor, cute little squeaky mice
are being gobbled up by mean, nasty cats that
are ten times their size!”
a. ambiguity
b. appeal to pity
c. burden of proof
d. slippery slope
Example: Colin Closet asserts that if we allow
same-sex couples to marry, then the next thing
we know we'll be allowing people to marry their
parents, their cars and even monkeys.
a. black-or-white
b. ad hominem
c. slippery slope
d. burden of proof
Example: After Sally presents an eloquent and
compelling case for a more equitable taxation
system, Sam asks the audience whether we
should believe anything from a woman who isn't
married, was once arrested, and smells a bit
weird.
a. bandwagon
b. ad hominem
c. burden of proof
d. composition/division
• Example: Bertrand declares that a teapot is, at
this very moment, in orbit around the Sun
between the Earth and Mars, and that because
no one can prove him wrong, his claim is
therefore a valid one.
a. black-or-white
b. composition/division
c. ambiguity
d. burden of proof
• Example: The witchcraft problem is the most
urgent challenge in the world today. Why?
Because witches threaten our very souls
a. ambiguity
b. black-or-white
c. begging the question(circular
reasoning)
d. bandwagon
• Example: The fallacy of offering reasons or
conclusions that have no logical connection to
the argument at hand (e.g. “The reason I flunked
your course is because the government is now
putting out purple five-dollar bills!”)
a. non sequitur
b. bandwagon
c. composition/division
d. ambiguity
• Example: An irrelevant distraction, attempting to
mislead an audience by bringing up an unrelated, but
usually emotionally loaded issue. E.g., "In regard to my
recent indictment for corruption, let’s talk about what’s
really important instead--terrorists are out there, and if
we don't stop them we're all gonna die!"
•
a. red herring
b. composition/division
c. black-or-white
d. false cause
• Example: Whilst rallying support for his plan to
fundamentally undermine citizens' rights, the
Supreme Leader told the people they were either
on his side, or they were on the side of the
enemy.
a. straw man
b. bandwagon
c. black-or-white
d. slippery slope
• Example: The fallacy of attempting to refute an
argument by attacking the opposition’s personal
character or reputation, using a corrupted
negative argument from ethos. "He's so evil that
you can't believe anything he says."
a. bandwagon
b. slippery slope
c. false cause
d. ad hominem
•THE END