• Two categories of fallacies:
• Category 1—Fallacies that have irrelevant
• Category 2—Fallacies that have unacceptable
• genetic fallacy—arguing that a claim is true or false
solely because of its origin.
– Example: We should reject that proposal for solving the current welfare
mess. It comes straight from the Democratic Party.
• composition—arguing that what is true of the parts must
be true of the whole.
– Example: The atoms that make up the human body are invisible. Therefore,
the human body is invisible.
• division—arguing that what is true of the whole must be
true of the parts.
– Example: This machine is heavy. Therefore, all the parts of this machine
• appeal to the person (or ad hominem, meaning “to
the man”)—rejecting (or accepting) a claim by citing
the person who makes it rather than anyhting about
the claim itself.
– Example: We should reject Chen’s argument for life on
other planets. He dabbles in the paranormal.
Accusation of inconsistency
Poisoning the well
Appeal to Authority
• equivocation—the use of a word in two different
senses in the same argument.
– Example: Only man is rational. No woman is a man.
Therefore, no woman is rational.
• appeal to the masses/popularity—arguing that a
claim must be true merely because a substantial
number of people believe it.
– Example: Of course the war is justified. Everyone
believes that it’s justified.
• appeal to tradition—arguing that a claim must be
true just because it’s part of a tradition.
– Example: Acupuncture has been used for a thousand
years in China. It must work.
• appeal to ignorance—arguing that a lack of
evidence proves something. This often shifts
the appropriate burden of proof
– No one has shown that ghosts aren’t real, so
they must be real.
– No one has shown that ghosts are real, so they
must not exist.
• appeal to emotion—the use of emotions as premises
in an argument.
– Example: You should hire me for this network analyst
position. I’m the best person for the job. If I don’t get a job
soon my wife will leave me, and I won’t have enough money
to pay for my mother’s heart operation. Come on, give me a
• red herring—the deliberate raising of an irrelevant
issue during an argument.
– Example: Every woman should have the right to an abortion
on demand. There’s no question about it. These anti-
abortion activists block the entrances to abortion clinics,
threaten abortion doctors, and intimidate anyone who
wants to terminate a pregnancy.
• straw man—the distorting, weakening, or
oversimplifying of someone’s position so it
can be more easily attacked or refuted.
– Example: Senator Kennedy is opposed to the
military spending bill, saying that it’s too costly.
Why does he always want to slash everything to
the bone? He wants a pint-sized military that
couldn’t fight off a crazed band of terrorists, let
alone a rogue nation.
• begging the question (or arguing in a
circle)—the attempt to establish the
conclusion of an argument by using that
conclusion as a premise.
– Example: God exists. We know that God exists
because the Bible says so, and we should
believe what the Bible says because God wrote
• false dilemma—asserting that there are only two
alternatives to consider when there are actually
more than two.
– Example: Look, either you support the war or you are a
traitor to your country. You don’t support the war. So
you’re a traitor.
• slippery slope—arguing, without good reasons, that
taking a particular step will inevitably lead to a
further, undesirable step (or steps).
– Example: We absolutely must not lose the war in
Vietnam. If South Vietnam falls to the communists, then
Thailand will fall to them. If Thailand falls to them, then
South Korea will fall to them. And before you know it, all
of Southeast Asia will be under communist control.
• hasty generalization—drawing a conclusion about a
whole group based on an inadequate sample of the
– Example: The only male professor I’ve had this year was
a chauvinist pig. All the male professors at this school
must be chauvinist pigs.
• faulty analogy—an argument in which the things
being compared are not sufficiently similar in
– Example: Dogs are warm-blooded, nurse their young,
and give birth to puppies. Humans are warm-blooded
and nurse their young. Therefore, humans give birth to