Download Logical fallacies - Uplift North Hills

Errors in Logic Often Found in
Persuasive Texts
A fallacy is an error in logical reasoning in an
argument or a persuasive text.
This isn’t the same as a “factual error.”
FALLACY
FACTUAL ERROR
4 out of 5 dentists
Chewing gum is made out
recommend Chewy Brand
of Silly Putty
Gum
There are many different types of fallacies,
and readers should be able to identify fallacies
when they occur in text.
Ad Hominem
Hasty
Generalization
Exaggeration
Appeal to
Emotion
Appeal to
Authority
Begging the
Question
Post Hoc
One of the most common forms of fallacy is
called an ad hominem argument. Literally, ad
hominem means “against the person.”
Instead of using logic in an argument, sometimes
people attack their opponent. That’s effective,
but fallacious!
EXAMPLE:
Teacher: Education is important.
We should spend more to improve
our schools.
Student: Of course you think that.
You’re a teacher.
Another common fallacy is the Hasty
Generalization. That’s when a person makes
sweeping statements based on just a little
evidence.
Example: Every swan I’ve ever seen was white.
Therefore, all swans
must be white.
Sometimes the breakdown in logic is just funny...
A post hoc fallacy involves attributing a cause
and effect relationship without adequate
evidence. (Which is similar to a hasty
generalization.)
Example: My car was running fine until Jimmy
borrowed it. Now it makes a funny noise. He
must have done something to it.
One of the most common fallacies that comes up
in advertising is the Appeal to Authority. Just
because somebody famous has an opinion, that
doesn’t make it true!
Similarly, just because a doctor or a dentist says
something, that doesn’t make it true, either!
This is also called the Bandwagon Fallacy,
because people are encouraging you to “jump on
the bandwagon.” Everybody else is doing it! All
the cool kids are doing it! Don’t you want to be
like everybody else?
Is there a fallacy in this argument?
I was sick with a terrible cold for
several days. Then I took some
vitamin C, and I got better.
Therefore vitamin C is a cure for
colds.
Is there a fallacy in this argument?
I was sick with a terrible cold for
several days. Then I took some
vitamin C, and I got better.
Therefore vitamin C is a cure for
colds.
This is a post hoc fallacy. If you’ve been sick for several days, you
probably would have gotten better soon anyway!
Is there a fallacy in this argument?
Fox News criticized a recent report
on climate change, saying that they
did not report their numbers
accurately. But then, you’d expect
Fox News to find a way to attack
the research on climate change.
Is there a fallacy in this argument?
Fox News criticized a recent report
on climate change, saying that they
did not report their numbers
accurately. But then, you’d expect
Fox News to find a way to attack
the research on climate change.
This is a classic ad hominem attack! Just because Fox News has a bias
doesn’t mean they’re wrong!
Is there a fallacy in this argument?
My opponent in this election has
suggested that cutting business
taxes could improve the economy.
Do I really need to point out that
big businesses have paid for his
campaign?
Is there a fallacy in this argument?
My opponent in this election has
suggested that cutting business
taxes could improve the economy.
Do I really need to point out that
big businesses have paid for his
campaign?
This is another ad hominem attack. Getting money does not
automatically make a person wrong!
Is there a fallacy in this argument?
Four out of five dentists who chew
gum recommend Trident.
Is there a fallacy in this argument?
Four out of five dentists who chew
gum recommend Trident.
A classic appeal to authority. And how many dentists who DON’T chew
gum would recommend Trident?
Is there a fallacy in this argument?
Grades in school don’t mean
anything. Benny is an idiot, and he
makes straight-As!
Is there a fallacy in this argument?
Grades in school don’t mean
anything. Benny is an idiot, and he
makes straight-As!
A hasty generalization. There may be a lot of reasons why Benny
makes good grades.
Is there a fallacy in this argument?
There’s nothing wrong with
speeding. Everybody does it!
Is there a fallacy in this argument?
There’s nothing wrong with
speeding. Everybody does it!
An appeal to popularity. If all your friends were jumping off a bridge,
would you do that too???