Re: Fitch's paradox and OWA
From: Reinier Post <rp_at_raampje.lan>
Date: 17 Dec 2009 22:52:46 GMT
Message-ID: <4b2ab63e$0$28714$703f8584_at_news.kpn.nl>
Date: 17 Dec 2009 22:52:46 GMT
Message-ID: <4b2ab63e$0$28714$703f8584_at_news.kpn.nl>
Nilone wrote:
>Does Fitch's paradox prove an inherent contradiction in the open-world
I don't understand the paradox.
http://plato.stanford.edu/entries/fitch-paradox/
explains:
suppose that
(KP) all truths are knowable, i.e. can be known by somebody at some time
and
(NonO) not all truths are known now
then
(1) there is an unknown truth p
and then
(2) p is true and unknown is itself a truth
and hence, by KP,
(3) (p is true and unknown) can be known by somebody at some time
"However, it can be shown independently that it is impossible
to know this conjunction. Line 3 is false."
>assumption?