There's a difference between logical validity and the truth/falseness of the
premises. I suggest that Jerry look into a few basic books on logic.
Harry Gensler's Introduction to Logic is a nice one.
Edwina
----- Original Message -----
From: Gary Richmond
To: Peirce-L
Sent: Thursday, April 28, 2016 2:54 PM
Subject: [PEIRCE-L] Re: Three inference patterns
Jerry wrote:
The swan example:
Rule: All swans are white
Case: Jimmy is a swan
Result: Jimmy is white.
Except, all swans are not white. Some are black. But people thought swans
were only white long ago...or so they say. Also, given our awareness of
genetics, there was always the possibility that swans could have been
black...blue, even.
[, , ,]
So, is the deductive swan example necessary reasoning? Is it correct? Is
the intention of deductive reasoning and syllogisms in general to promote
correct reasoning or necessary reasoning?
The form of the syllogism is correct. For deductive reasoning the conclusion
will necessarily be true if the rule is true. In the swan example it is not
true that all swans are white, so the conclusion is not necessarily correct,
although its form most certainly is. This is pretty basic logic.
Best,
Gary R
Gary Richmond
Philosophy and Critical Thinking
Communication Studies
LaGuardia College of the City University of New York
C 745
718 482-5690
On Wed, Apr 27, 2016 at 5:45 PM, Gary Richmond <[email protected]>
wrote:
List,
Not to be taken too seriously--as this was just a bit of play which
occupied me for an hour or so today-- but based on the bean example, here's how
I see the three inference patterns and their paths (vectors) through the 3
categories.
Inference patterns and categoriality:
1ns, Result (for deduction only) == 'Character' (for abduction/induction)
|> 3ns, Rule
2ns, Case
Middle term: That which is the middle term in deduction is put in bold in
all 3 patterns
Vectorial order: In each case start at * and conclude at ***
Deduction (vector of involution):
***3rd, 1ns: conclusion-It is NECESSARY that Jesus die.
|> *1st, 3ns: All men die,
**2nd, 2ns: Jesus is a man;
Abduction (vector of representation):
**2nd, 1ns: Jesus died;
|> *1st, 3ns: I make the supposition that all men die,
***3rd, 2ns: conclusion-It is POSSIBLE that Jesus was but a man.
Induction (vector of determination):
**2nd, 1ns: Jesus dies;
|> ***3rd, 3ns: conclusion-It is PROBABLE that all men die.
*1st, 2ns: Jesus is a man,
Well, again, one doesn't want to make too much of this except to note that
both deduction and abduction begin with a rule (in abduction, a mere
'supposition'), while induction concludes with a rule (which has some
probability).
Best,
Gary R
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