From: Brian Holtz [brian@holtz.org]
Sent: Saturday, March 23, 2002 8:33 AM
To: alt.atheism.moderated
Subject: Re: Science & atheism are cultures.


"Jesse Nowells" <jnowells@transbay.net> wrote:

> > what does "non-existence" mean for a possible world?  "Existence"
> > or "actuality" is an indexical: to say that something "exists" or "is
> > actual" is just to say that it has a certain relationship (causal) to
> > the things in "this" (i.e. the indexed) world.
> 
> A possible world can possibly exist or not.

Under what definition of "exist"? You simply have not answered my
question.

> Signifying the possibility of improbable
> things signifies nothing except empty supposition.

It's hardly "empty supposition" to distinguish the impossible
from the possible-but-improbable.

> > for a possible world, "possible existence" and "actual
> > existence" (whatever the latter might mean) would be
> > indistinguishable, both to those outside that world and 
> > those inside it.
> 
> There is no actuality inside a non-existent world & there is 
> no actuality ouside of existing world.

I doubt that you can give non-question-begging definitions of
"actuality" and "existent/existing" that would make this
statement true.

> Actuality & possibility are not indistinguishable because 
> they don't have the same meaning

They of course have distinguishable meanings within a given
(possible or "the actual") world. But can you explain the
difference between them when used across (i.e. applied to)
possible worlds themselves?

> > This is what I meant by the analogy that the inhabitants
> > of a simulation could not tell the difference between the
> > simulation being run twice and the simulation being run never.
> 
> The inhabitants would never be instantiated in a simulation 
> that is never ran

But the possible inhabitants would still have their possible
thoughts, and those possible thoughts would appear the same 
to those possible inhabitants as actual thoughts would appear
to actual inhabitants. That is, the thoughts that are to
be thunk in a simulation do not change in content just by 
running the simulation.

> > But the possibility or actuality of an entire possible world 
> > may be a notion to which our usual within-world notions of
> > possibility/actuality cannot trivially be applied.
> 
> How is possibility or consideration of possibilities
> "within-world"  notions?

Within a world, "actual/existent" just means causally related
to the rest of the world, and "possible" means (as always)
not self-contradictory. So as applied to entire worlds,
"possible" again means not self-contradictory, but "actual/existent"
cannot mean causally related to the rest of "the" (or any) world, 
because worlds are defined as being causally separate.
So what does "actual/existent" mean when applied to entire
possible worlds?

> A possible world possibly exists & therefore if it exists is not
> within the actual world but *is* the actual world.

To say this you need a definition of "actual/existent" that when
applied to possible worlds shows that there could only be one
such world, and then you'd have to be able to show that the
world we perceive is not merely possible but is indeed "actual".
Good luck!
--
brian@holtz.org
http://humanknowledge.net