Re: Existence as predicate

From: Paul Holbach (paulholbachSPAMBAN_at_freenet.de)
Date: 09/07/04 

Date: 7 Sep 2004 13:10:10 -0700

> Kenneth Doyle <nobody@notmail.com> wrote in message news:<
> Xns955D74573C4C6nobodynotmailcom@61.9.191.5>...

> And for all we know, there might be a future king of France 100 years from
> now (at which time "the present king of France" will have a referrent).
>
> Is there some standard way of dealing with these sorts of situations, or do
> we just have to mind our "p"s and "q"s? For example, in the above
> paragraph, I almost wrote "there might be a present king of France 100
> years from now". To tie this back into the subject, I'm thinking that if
> existence is a predicate after all then perhaps it could serve as a
> temporal modifier. So we would have "exists now", "shall exist", "did
> exist" and even "might exist". Or something like that.

In order for you to be able to express the statement

"There might be a present king of France 100 years from now"

properly, you need to combine predicate logic, temporal logic, and
modal logic in a certain way.

Itīs really not easy to find an appropiate translation for an ordinary
language sentence like the one above, which seems pretty 'harmless'.

Letīs try it with a predicate-logic approach:

["n" : "now" / "ixKFx" : "the (present) king of France"]

<>Et[t = n+100y & Ex(x = ixKFx)(t)]

"It is possible that there is (will be) a time t such that t is 100
years away from now, and that, at t, there is somebody who is the
(present) king of France."

#PH

P.S.:

In the modal-logic approach to temporal logic, which has been
championed by Arthur Prior, tensed statements are usually expressed as
follows:

- "p" :<-> "It is now the case that p"
- "Fp" :<-> "It will/shall at some time be the case that p"
- "Pp" :<-> "It has at some time been the case that p"

For more information, see:

http://plato.stanford.edu/entries/logic-temporal

Relevant Pages

  • Re: Is "existence" a predicate?
    ... the things that satisfy the predicate and the things that don't. ... Existence doesn't do this, because _everything_ exists! ... the present king of France, ...
    (sci.logic)
  • Re: Is "existence" a predicate?
    ... the things that satisfy the predicate and the things that don't. ... Existence doesn't do this, because _everything_ exists! ... the present king of France, ...
    (sci.logic)
  • Re: Is "existence" a predicate?
    ... the things that satisfy the predicate and the things that don't. ... then there are non-existent things, For example the described object, ... the present king of France, ...
    (sci.logic)
  • Re: Is "existence" a predicate?
    ... the things that satisfy the predicate and the things that don't. ... Existence doesn't do this, because _everything_ exists! ... the present king of France, ...
    (sci.logic)
  • Re: Is "existence" a predicate?
    ... the things that satisfy the predicate and the things that don't. ... then there are non-existent things, For example the described object, ... the present king of France, ...
    (sci.logic)
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