CS 100 - Week 12 Lecture 1 - 11-6-12

starting Chapter 8!
Evaluating Arguments and Truth Claims

When IS an argument a "good" argument?
...from a CRITICAL THINKING standpoint;

...what "good argument" does NOT mean:
*   "good argument" does NOT mean "agrees with my
    views"

*   "good argument" does NOT mean "persuasive
    argument"

*   "good argument" does NOT mean "well-written"
    or "well-spoken"

what DOES "good argument" mean, then,
FROM a critical thinking standpoint?
*   ...it is an argument that satisfies the relevant
    critical thinking standards that apply in a
    particular context;
    *   the MOST IMPORTANT of these standards are:
        *   ACCURACY (e.g., are the premises true?)
        *   LOGICAL CORRECTNESS
	    is the reasoning correct?
	    is the argument deductively valid
	                 OR inductively strong?
    *   BUT, OTHER critical thinking standards
        should ALSO be taken into account, including:
        *   CLARITY
        *   PRECISION
        *   RELEVANCE
        *   CONSISTENCY
        *   COMPLETENESS
        *   FAIRNESS

Going with this definition/idea of a good argument,
here are some general guidelines for evaluating
arguments:
*   are the premises true?
*   is the reasoning correct?
    is the argument deductively valid?
                    inductively strong?
*   does the arguer commit any logical fallacies?
*   are the premises relevant to the conclusion?
*   does the arguer express his/her points
    clearly and precisely?
*   are the arguer's claims logically consistent?
*   is the argument complete? (reasonably complete,
    given the context? is there relevant/important
    evidence being left out?)
*   is the argument fair? (fairly representing the
    opposing side's views, for example -- as another
    example, are they presenting the evidence fairly?)

moving on, then --
since it IS such an important criterion in the
"goodness" of an argument,
let's talk about:
When IS it reasonable to accept a premise as true?

*   this is NOT the whole SHEBANG --
    this is a complex issue,
    we're just giving a few SUGGESTIONS here,
    (and we'll be adding a few more over the
    next few chapters)

*   for the sake of THIS discussion,
    let's consider:
    WHEN is it reasonable to accept an asserted 
    claim, that is unsupported,
    and that for some reason it is either
    IMPOSSIBLE or not worthwhile to try to verify
    the claim for ourselves;

    WHEN, then -- under what conditions --
    is it REASONABLE to accept such a claim?

*   there are general principles,
    ALTHOUGH they have a few known trouble spots;

    sometimes called the principles of
    rational acceptance:
    *   generally speaking, it is reasonable to
        accept a claim IF:
        1. the claim does NOT conflict with personal
	   experiences that we have no good reason
	   to doubt
   
        2. the claim does NOT conflict with BACKGROUND
           beliefs that we have no good reason to
	   doubt

        3. the claim comes from a credible source
   
moving on yet again...
Refuting arguments
*   to REFUTE an argument is NOT merely to
    challenge it, rebut it, or criticize it --

    it is to DEFEAT it,
    to show that its premises do NOT provide
    convincing reasons to accept the conclusion

*   you can criticize an argument in MANY ways,
    but there are only TWO ways to refute one:
    1.  Show that a critical premise -- or
        a critical group of premises -- is
	false OR dubious

        [e.g., what's the key support, in
	a structural sense?]

        *   to show an argument is dubious:
            *   appeal to personal experience
            *   or to common knowledge
            *   or to a reputable information source
            *   or note that a premise is
	        self-contradictory
            *   or point out if one premise
	        conflicts with another
            *   show that a premise is based
	        on an unwarranted assumption
		or stereotype
            *   personally demo that the claim is
	        false or dubious

        ...also:
        *   reducing to the absurd
            reductio ad absurdum
            *   show a statement is false
	        by proving it logically implies
		something that is clearly false
		or absurd

        *   refutation by counterexample
            *   esp. for "All A's are..."
	        statements
		...if you can give ONE example
		of an A that isn't, you've
		refuted that statement!

    2.  Show that the conclusion does not
        follow from the premises
        *   deductive: does the conclusion
	    NECESSARILY lead from the premises
        *   are the premises relevant to conclusion?
	*   are they sufficient?