On May 5, 2007, at 10:13 AM, Waclaw Kusnierczyk wrote:
> ...Pat says that logic is a theory of truth (or Truth?). (01)
No, he says that (classical first-order) logic includes a component
(namely, model theory) that includes a theory of truth (namely,
Tarski's). This theory of truth is actually quite mundane -- it is a
surprisingly simple and straightforward definition of truth as it
pertains to formal languages and their interpretations that seems to
capture much of what we have in mind by word "true" in the ordinary
sense. It tells us nothing whatever about big-T Truth, assuming the
big-T there is supposed to signify Something Profound. (02)
> So logic is a theory of Logic, but it is not Logic. (03)
Huh? What is this big-L Logic whereof you speak? (04)
> If something is logically incoherent, it still does not prove, in
> any way or sense, that it is also inconsistent with Logic. (05)
How would we know if you aren't telling us what Logic is? (06)
> Same response to Chris: that your logic (*the* logic, if you
> prefer) forces you to conclude that god is devil, and that this is
> inconsistent, this does not prove (otherwise than in that logic)
> that being god and devil at the same time is incoherent. Perhaps
> stating this in logic (with appropriate assumptions) leads to
> inconsistence, but that's all.
>
> I am not hereby defending the view that there is god, or any other
> compatible or contradictory view, for that matter. My point is
> that logic is a theory, (07)
This is sounding ominously like the claim that evolution is (just) a
theory. (08)
> and thus it is, in principle, as good as any other theory, in that
> it may well be incorrect. (09)
Well, not if it *is* correct. So what do you mean exactly? That a
logical theory, qua theory, is falsifiable? But how would you
falsify, say, the law of noncontradiction? How would you do that?
Wouldn't you have to provide an argument that *assumes* that
noncontradiction is valid? Or do you find arguments of the form
"P&~P, therefore Q" rationally persuasive grounds for believing Q? (010)
There are, of course, logical systems in which certain classical
principles do not hold across the board -- intuitionists, for
example, reject excluded middle and paraconsistent logicians reject
the general validity noncontradiction to accommodate paradox (though
they do *not* accept the validity of the argument form above). So
yes, there can be philosophical reasons for rejecting the general
validity of certain classical principles. But these reasons are
based upon a priori, philosophical views about the nature of the
basic concepts of logic -- intutionists, notably, argue from a very
distinctive (non-realist) philosophical position about truth and the
nature of mathematics. But to think that logic, no matter which you
prefer, is falsifiable in the way that, say, Newtonian Mechanics is,
is simply a mistake. In logic we start with principles whose
validity we accept a priori and we build our systems to reflect them
after the fact. We do not derive them empirically by observation and
test them with laboratory experiments. (011)
> That it it is unimaginable for us that there could be world in
> which logic as we know it would not be an appropriate theory of
> truth is closer to blindness than to omniscience. (012)
Well, *that* is certainly nothing more than an article of faith on
your part, since you haven't provided the least reason to think there
is actually something there to be seen. But if you want to believe
there are worlds where every contradiction is true and people can
truly believe six impossible things before breakfast, far be it from
me to try to talk you out of it. :-) (013)
-chris (014)
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