Re: OUTGOEDELING A HUMAN?

On Feb 23, 10:08 pm, stevendaryl3...@xxxxxxxxx (Daryl McCullough)
wrote:

Sorry, this is my last post, since I'm leaving on vacation for a week.
abo says...

What are you seeking?

I'm claiming that "true" doesn't have an absolute meaning,
and neither does "corresponds with the way the world is".
Does "This sentence is not true" correspond with the way
the world is, or not?

It does not.


It helps in the sense that it is a *consistent* approach to
reasoning about sentences that mention truth. Most other
approaches are inconsistent.

There are plenty of *consistent* approaches.

Well, I want an approach that as much as possible allows us to
do normal reasoning of the form

All Xs are Ys.
No Y is a Z.
Therefore, no X is a Z.

An approach with inference rules that have a caveat saying
"This rule is not to be used if it would result in a paradox"
is pretty worthless as an inference rule. The point of sound
inference rules is that *if* your premises are
true, *and* you follow the rules, then your conclusions will be
true. That way, if you ever derive a contradiction, you know that
at least one of your premises was false.

Once you start putting in exceptions, then you *never* know
whether your premises were faulty or not. Take the Liar, for
example. What basis is there for saying that it is paradoxical?
The usual approach is to assume that the Liar is true, and show
that that leads to a contradiction, and then to assume that it
is false, and show that *that* also leads to a contradiction.
If your rules of inference have an exception "Never use this
rule to conclude a contradiction" then how do you ever demonstrate
that the Liar is paradoxical, in the first place?

The alternative that you are suggesting is not a real alternative.
It can't actually be used to do reasoning. Perhaps you can make it
consistent by forbidding paradoxical conclusions, but then you've
made your reasoning practicaly impotent.


When I said one can block the inference, I didn't mean that one is
blocking a logically valid inference. That of course would be ad hoc
and close to (if not actually) inconsistent. The inference from ""This
sentence is paradoxical" is paradoxical" to ""This sentence is
paradoxical" is true" depends on an assumed property of truth, given
by the schema if S, then "S is true." One can reject the validity of
the schema (which is not a logical validity) and block the reasoning.
Of course, one then has to explain *why* one can reject this. As this
is my last post for the moment, I'll have to refer to postings that I
made to sci.logic about 8 years ago, which I regrouped here:

http://www.andrewboucher.com/papers/paradoxes.htm

Here's a link to the first sci.logic post (incidentally, you were part
of the discussion);

http://tinyurl.com/yto7jo





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