Download What is a fallacy? Remember Logic?

Fallacies:
An Introduction
 Define fallacy
 Classifications of
fallacies
 Valid vs. Sound
arguments
 Important notes
What is a fallacy?
A mistake in reasoning
An incorrect
argument in
logic and rhetoric
lack of validity
or
lack of soundness
A fallacious argument is
an argument that contains
a mistake in reasoning
Remember Logic?
 Syllogism: a systematic arrangement of arguments,
consisting of:
Categorical Disjunctive Conditional
a major premise
Every A is a B. Either A or B.
If A is C.
a minor premise
Every C is A.
Not A.
And C is B.
Therefore, B.
Then A is B.
a conclusion
Therefore: Every C is B.
 Enthymeme: A truncated syllogism where one or more of
the premises is implied.
major premise
minor premise
conclusion
major premise
minor premise
conclusion
major premise
minor premise
conclusion
major premise
minor premise
conclusion
 An enthymeme calls upon the audience’s existing
beliefs for one or both of its premises.
Fallacy Classifications
Reasoning
Deductive General conclusion  Specific cases
Inductive Specific cases

General conclusion
Formality
Formal
Error in structure (form) Septuagenarians are
people in their seventies.
Informal
Error in content
If A is C.
And D is B.
Then A is B.
My mother is in her
seventies.
Thus, my mother is a
septuagenarian.
Difference between:
Valid arguments: refers to “form”
Sound arguments: must meet all of the
following criteria:
The premise(s) of the argument must be true
The conclusion must follow from the premises
The content of the argument must be free of
fallacies
Remember: An argument containing a
fallacy may still be correct -- by chance!
Students who come to class usually do well in my class.
Your attendance is poor in my class.
Therefore, you must not be doing well in my class.
Important Notes
 Who can commit a fallacy?
Speakers / Senders
Listeners / Receivers
 Fallacies can be intentional or unintentional
 Names of fallacies may differ
It is not enough to be able to name the
fallacy
It is important that you be able to explain
why an argument is fallacious
 Fallacies can overlap
Processing Time!
What is a fallacy?
What does formal logic
have to do with fallacies?
Is a valid argument
necessarily true? Or a
sound argument?