Philosophy
6: Logic in Practice
Los Angeles Pierce College
Department of History, Philosophy, & Sociology
Lecture Notes
Lecture Notes for
"Chapter Four" of Porter's The
Voice of Reason
Part One: Disagreements
Types of
Disagreement: Factual and Verbal
Understand that we are
here engaged in argument identification
First step, isolate
disagreements
With disagreement
isolated, we know what we must support
Types of Disagreement: Factual and Verbal
Is!/Is Not!
vs.
Potato/Potato
Factual Disagreement
What is the case?
What is not the case?
Factual Disagreement E.G.s
The number of civilian
deaths since the beginning of the second Iraq war is at least 99,712
No, others say it
surpassed 500,000
Resolution
Objective evidence is
needed to support claims about facts
Credible authorities can
supply such facts
Difficulties w/ Resolution
But when evidence is hard
to find, resolution can be elusive
Difficulties w/ Resolution E.G.
Global warming
Verbal Disagreements
"A verbal
disagreement is another kind of dispute, involving a difference of opinion over
what crucial words mean"
Verbal Disagreements
E.G.s "You're such a drug addict!"
"You smell like a
____."
Some Causes of Verbal Disagreement
"People may have been
taught to use a word differently so that the intensional
meaning is unusual, or nonnative speakers may have a different extension for
the word in their own language"
Resolving Verbal Disagreements
Define your terms!
"We must keep in mind
the various types of definitions, whether stipulative,
reportive, synonym, or
example, and use the one appropriate to our subject"
Interpretive and Evaluative Disagreements
Deeper problems lurk here
Interpretive Disagreements
"Interpretive
disagreements do not concern words but are disputes about how events or actions
should be construed, how stories, art, speeches, historical episodes, and so
forth should be taken"
Interpretive Disagreements E.G.
"To take an everyday
example, suppose that someone you know passes by without saying hello. Should you interpret this as a
deliberative snub, that the person 'cut you dead,' or should you assume the
person was preoccupied, 'absent-minded?'"
Causes of Interpretive Disagreements
Particular points of view
Differing perspectives
Resolving Interpretive Disagreements
"In trying to find
the best interpretation of these events, the stand we should us is
plausibility. That is, we have to
build a case showing that a particular interpretation best explains a
situation"
Differing Interpretations
Seemingly equally good,
but mutually exclusive interpretations
They can't both be true
(usually)
Problems w/ Resolving Interpretive Disagreements
In persuasive arguments,
interpretational vagueness can be intentional
Evaluative Disagreements
Evaluative disagreements
stem from disputants who differ in their "claiming that something should
be considered good or bad"
Evaluative Disagreements
E.G.s The consumption of drugs is bad
Resolving Evaluative Disagreements
Inconsistencies
Consequence
Consensus
Resolving Evaluative
Disagreements / Inconsistencies
"How can you not like
this, you claim to love all things X"
Resolving Evaluative
Disagreements / Consequence
"we can show how our
position would lead to good results and the opposite position would have
undesirable consequences"
Resolving Evaluative
Disagreements / Consensus
"An even more
positive method of reaching agreement about value judgments is to point to some
moral consensus that exists beneath the level of the dispute"
"if we can all agree
on some basic values that underlie those in dispute, we can build upward from
that common ground"
Tying It Out
I. 3
I. 5
I. 6
I. 8
I. 10
Part Two
Reasoning Things Out
Relevance in Arguments,
Adequate Truth, and Alternative Possibilities
Relevance
Relevance "refers to
whether the reasons or evidence apply to our conclusion"
True justification
relevant justification
E.G.s of Irrelevance
He is a good knitter
because he has a good ear for music.
Here, "the reasons we
give are irrelevant to the claim they are supposed to support."
Problems w/ Relevance
Determining relevance can
be quite difficult
Answers w/ Relevance
"The fact of twilight
does not make it impossible to differentiate night and day"
Adequacy
How much evidence is
needed?
As much as possible,
within reason
Inadequate
Inadequate evidence when,
"the base is much too narrow to support the conclusion"
E.G.s of Inadequate Proof
"Sometimes we hear
people claim that there's no link between smoking and cancer because an uncle
or grandfather smoked three packs a day and lived to age 94"
Adequacy Relevance
"In the case of
smoking, our uncle's longevity certainly applies to our claim, but it's just
not enough to warrant it. We would
need a lot more evidence before anyone would be convinced"
Generalizations & Exceptions
Singular instances of
contradictory occurrences are usually inadequate to disprove a generalization
The opposite is the case:
exceptions can show a generalization to be accurate
So Far
"the overall point
[so far] is that in our arguments we need evidence that is adequate to prove
our case as well as evidence that is true and relevant"
Alternatives
Arguments for one
procedure that may work can nevertheless not be desirable, especially when
there are alternative ways of proceeding that also work
"No one would doubt
that the guillotine is an infallible remedy for migraines headaches. It would certainly be effective, but at
too high a price"
"although an action
may work, that does not mean it is the best way of solving a problem"
Alternatives E.G.
Argument to cut costs in a
large manufacturing firm
Action:
Lay off "older,
higher salaried employees whose productivity is decreasing"
Argument:
Saves money
Increases competitive edge
Not a charity anywho
Alternatively,
Action:
Incentivize early
retirement, or offer half-time contracts
Argument:
Money can be saved by
other means
Loss of "most
experienced" will affect others' loyalty, commitment, and morale
Loss of institutional
knowledge
"Even if firing older
employees would be effective, it may not be the best policy"
Again, "although an
action may work, that does not mean it is the best way of solving a
problem"