Ling 21:
LANGUAGE & THOUGHT
Lecture 2:
Recognizing Arguments
ARGUMENT STRUCTURE
 Logic: The study of arguments
 An argument is a sequence of statements –
– One is the conclusion to the others.
– All the others are premises.
 The premises provide evidence for the
conclusion.
EXAMPLES
 All humans are mortal.
Brad Pitt is human.
Ergo, Brad Pitt is mortal.
 Sarah was not at the party.
Ergo, it couldn’t have been Sarah that Jack
was dancing with.
FORMAL vs INFORMAL LOGIC
 Formal logic: the study of argument forms –
abstract patterns common to many different
arguments.
valid
If P, then Q
P
Ergo, Q
invalid
If P, then Q
Q
Ergo, P
 Informal logic: the study of particular arguments in
natural language
PREMISES
 Premises and conclusions are always
propositions (statements) – they can be true
or false.
 They are not questions, commands or
exclamations.
– Test: “It is true / not true that P”
where P = a premise or a conclusion
EXAMPLE
It is true that Sarah was not at the party.
*It is true that Where was Sarah?
*It is true that Don’t you dare do that again!
Note: /*/ indicates that a statement is unacceptable.
Exercise: Identifying statements. (ex. 2.1, p. 33)
NOTE 1
At issue is the form of the statement,
whether it CAN be true or false,
not whether it IS true of false.
These are PROPOSITIONS:
Snow is green.
I am Brad Pitt.
These are NOT:
*What color is snow?
*Hey, look, there’s Brad Pitt!
NOTE 2
Although the premises, by definition, provide
evidence for the conclusion, this evidence
may be good or not.
You have to let me go to the party;
everyone is going to be there.
NOTE 3
 In standard form, the conclusion appears at the
end.
 In practice, the conclusion may appear anywhere.
Jack could not have been the murderer.
The victim was shot from 40 feet away.
Jack is blind and paralyzed from the neck
down.
Exercise: Identify premises and conclusions of
arguments. (ex. 2.2.1, p. 37)
CONCLUSIONS INDICATORES
Inference indicators: Indicate the role of a proposition in
an argument.
Conclusion indicators:
There are no lights on. _____ no one is home.
Therefore
Thus
Hence
So
For this reason
Consequently
It follows that
Which proves/means that
AS a result
PREMISE INDICATORS
Premise indicators:
____ there are no lights on, no one is home.
Since
Because
Assuming that
Seeing that
Granted that
In view of the fact that
Inasmuch as
CAUTION
Conclusion and premise indicators don’t always
indicate conclusions and premises:
*It has been ages since I ate really good sushi.
*She’s so cute!
Exercise:
Identify premise/conclusion indicators.
(ex. 2.2.2, p. 37)
IMPLICIT STATEMENTS
Sometimes arguments are not actually
expressed or may be expressed incompletely.
One of us will be cleaning the bird cage, and it
won’t be me.
Implicit conclusion: You will be cleaning the
bird cage.
Alisha wears Birkenstocks, which proves that
you don’t have to be a tree-hugger to wear
Birkenstocks.
Implicit premise: Alisha is not a tree-hugger.
IMPLICIT ARGUMENTS
 Rules governing reading propositions into an
argument
– Do so only if it is required to complete the
arguer’s thought.
– Do so only if the arguer would accept the
proposition.
– Employ the principle of charity – give the arguer
the benefit of the doubt and make the argument
as strong as possible.
– Minimize misrepresentation.
NON-ARGUMENTS
1.
2.
3.
4.
5.
Reports
Unsupported Assertions
Conditional Statements
Illustrations
Explanations
REPORTS, ASSERTIONS
 Reports convey information
 Unsupported assertions are statements of
what a speaker or writer happens to believe.
CONDITIONAL STATEMENTS
 Conditional statements (if-then statements)
– Antecedent and consequent sometimes
implicit:
Should it rain, the picnic will be cancelled.
Pete will graduate provided he passes
calculus.
– May be parts of arguments
but are not themselves arguments.
ILLUSTRATIONS
 Illustrations: provide examples of a claim but
do not prove or support it.
Many wildflowers are edible.
For example, daisies and day lilies are
delicious in salads.
 There are borderline cases between examples
and evidence.
Many of the world’s greatest musicians
died at 27. for example, Jim Morrison,
Janis Joplin, Jimi Hendrix and Curt Cobain.
EXPLANATIONS
Explanations: try to show why something is
the case, not to prove that it is the case.
The Titanic sank because it hit an iceberg.
(Explanation)
Capital punishment should be abolished
because innocent people may be mistakenly
executed. (Argument)
EXPLANATIONS – 4 TESTS
1. The common knowledge test
2. The past-event test
3. The author’s intent test
4. The Principle of Charity test
COMMON KNOWLEDGE TEST
Is the explanandum (what is being explained)
a matter of common knowledge?
(Why would you try to prove something that
is widely accepted as fact?)
Many musicians die young because they ‘live
hard.’
PAST EVENT TEST
Is the explanandum an event that occurred in
the past?
Mel flunked because he never went to
class.
AUTHOR’S INTENT TEST
 Is the author trying …
– To provide evidence for accepting the claim as
true
or
– To offer an account of why an event occurred or
why something is as it is?
Kevin is majoring in PoliSci because he wants to
go to law school.
PRINCIPLE OF CHARITY TEST
The Principle of Charity requires that we
interpret unclear passages generously.
Here that means not interpreting a passage as
a bad argument when it would be
reasonable to interpret it as a good
explanation.
CAUTION
 Not foolproof.
No single shooter could have shot as quickly
and as accurately as Oswald is alleged to
have done in the Kennedy assassination.
Therefore Oswald was not the lone shooter.
Exercise: Identify arguments and explanations
(ex. 2.4.1, p. 48)