From: cash@convex.com (Peter Cash)
Newsgroups: sci.physics,sci.philosophy.tech,talk.religion.misc
Subject: Re: Non-Existence of Existence (and God,too).
Date: 31 Jul 92 17:57:05 GMT
Organization: The Instrumentality
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In article <1992Jul31.154324.22928@news.media.mit.edu> minsky@media.mit.edu (Marvin Minsky) writes:
...Some very interesting things...

>  To say that a certain object exists is like saying that it's in the
>universe.  There isn't anything wrong with that.  But then, to say
>that the @i[universe] exists is saying that the universe is inside
>itself - which makes no sense at all.  And the trouble is that the
>ordinary way of saying things like "X exists" is a useful shortcut
>that causes trouble when you try to think more about it, because what
>we really should say is not a simple predicate E(x) at all, but a
>relation IN(x, U) -- that is, we should say X is in Universe U.

Let me see if I understand you correctly. I take you to be saying that "X
exists" is shorthand for something. The expanded sentence would read, "X is
in class U." Hmm. In that case, what is U? Well, U is the class of all
things that are contained by ... U. But then what is the informational
content of asserting "IN(x,U)"? Well, just that X is a member of some class
U.

The trouble with this is that I had always thought that one is saying
something informative (or, at any rate, attempting to say something
informative) when one asserts that a thing exists. But now it looks as
though saying that "Unicorns exist" is to assert that unicorns are the
members of some class of things. But what characterizes this class?
Nothing--other than that it has (at least one) member. Are horses also a
member of this class? According to the criteria you've given, I can't say.
I might be able to say if you gave me some characteristic that all members
of class U have in common--but you don't want to do that, since that would
make existence a predicate. (This is all vaguely familiar--I do wish I had
paid attention in logic class.)

>    To see why this is serious, imagine the predicament of a person
>like Tron (or you, or me) that is actually being simulated by a
>Virtual Reality Program inside some computer C.  I'm not joking.
>Clearly, you couldn't tell whether you were absolutely "real" or
>'just' a program inside some computer C.  Because there's no way to
>detect C itself.

I fail to understand what connection this story -- interesting as it may be
-- has with the previous argument. In what way is the question "Am I a
computer program?" like "Do I belong in class U?". The interesting question
here isn't whether I exist, incidentally--the interesting question is what
_sort_ of thing I am.
...
>And we can make the
>same statements about each of these "grades of existence":
>   --P runs inside some actual computer
>   --P runs only in the mind of its human programmer.. 
>   --P doesn't run at all, but just sits there on paper. 
>   --P isn't even written, but only imagined by someone. 
>   --P isn't even imagined, but merely a "possible" program, not yet even 
>conceived by anyone.

I really like these examples--though perhaps not for the same reason you
do. I like them because they show up the fogginess of asking, "What is
existence?" The question has no meaning outside a context.

What does someone mean who asks, "Does the Pswitch program exist?"? It all
depends on what he wants to know. If my boss is asking me this, then it
will not likely do if I reply, "Yes, it exists as an idea in my mind". My
boss wants the program written, tested and running--and he wants it NOW.

Then again, maybe the person asking the question is the local sysadmin, and
he wants to know if a Pswitch process is currently running somewhere on
the network. To say, "Yes, it lives in the /usr/local/bin directory is
_not_ satisfactory--as far as he's concerned, the program only exists if
it's running. 

Maybe the question is being asked by one of the developers on my project
team. In that case, it might do if I say, "Well, I haven't written it yet,
but I have the algorithm in my head."

>    In each such case, if P describes some simulated universe, there
>is no way for the creatures inside that universe to know whether or
>not their universe "actually exists" as a feature inside some larger
>universe.  No answer to such a question could have any actual
>consequences -- and therefore, the attribute of existence is an
>inconsequential accessory!  There is no possible way to prove that our
>universe itself is anything more than a "logical possibility".  

I don't follow how you arrive at this conclusion.

>So all
>that religious garbage about "who created ..." is based on a simple
>mistake, of postulating an unnecessary entity.

Ditto.
-- 
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
             |      Die Welt ist alles, was Zerfall ist.     |
Peter Cash   |       (apologies to Ludwig Wittgenstein)      |cash@convex.com
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~