Re: Category Theory and Rosen - some clarifications (i hope 8-))

[glen e. p. ropella]

Barry McMullin writes:
 > I am *not* going to argue about how to "define" the word "ALife" 
 > (phew!).  

OK.

 > I just want to point out that there is a class of systems
 > (call this class what you will) that I am fascinated by, that are
 > *sometimes* classified somewhere within ALife, that I think
 > Rosen *may* have been trying to model/formalise, and which do *not*
 > meet this criterion of Glen's.

We'll see about that.  Whether they are a class of iterated systems,
I mean.

 > What are they?
 > 
 > Well, accept Glen's "bag of stuff" as identifying something I will call
 > a "universe".  Embedded within this universe there may well
 > be "systems" (NB: *not* "sub" systems!) with the property that, over time,
 > they turn over their components ("pieces of stuff"), while preserving 
 > their own integrity and organisation (the relation to "life" should be 
 > obvious).  I claim that we could have a *perfect* 
 > model/understanding/formalisation of this *universe* without knowing
 > *anything* about these embedded systems (not even
 > that they exist, or how to look for them, or how to interact with them).
 > 
 > Note in particular that these systems are not, in any reasonable sense,
 > "sub" systems, or "sub" bags of stuff, precisely because their 
 > constituent "stuff" is constantly changing.

This is an important criterion.  But, having fluctuating constituents
does not mean that it's not iterative.  And it doesn't even mean that
it's not a "bag of stuff".  I don't really want to degenerate too far
into this; but, "stuff" doesn't have to be "particles".  Stuff can
consist of just about anything.  So, even if the stuff globs up into
particles for a little while, it can de-glob anytime it wants.

You seem to be talking mainly of "dissipative" or "open" systems.
These are *still* iterative systems.

 > In short, what I am crying out for is a useful formalisation for dealing
 > with things that are absolutely *not* "bags of stuff".

Yes, you want something to deal with things that are not made
up of [state, boundary conditions, dynamics], that's for sure.

 > The funny thing is that virtually all of what we currently call exact, or
 > hard, science, can deal *only* with "bags of stuff".

This is true, given your limited use of the word "stuff".  But, I will
still claim that backing off of both "closed" systems (what you're 
thinking of as "bags of stuff") and "open" systems (where the 
constituents are mutable) and considering that both are iterated
systems.

 > PS: Just to further muddy the waters: I think the systems I have tried
 > to identify go outside the scope of what Glen called "bags of stuff"; but,
 > I also think the class of systems Rosen is interested in go *even further
 > still* (in brief, where not even the "universe" they are embedded in can be
 > regarded as a "bag of stuff"). So I seriously differ with Glen when he
 > says his idea of a "bag of stuff" might be "broader" than the class
 > of systems Rosen wants to consider...

Again, you're concentrating too much on the idea that the "stuff" in a
"bag of stuff" is matter or atomic.  Think of a bag of stuff as more
like the "ambience" around us where the stuff can be divided and
parsed in an infinite number of ways.  That's the way I used the
phrase.

Is there anything you can say that will give an understanding of
the difference between a "sub-" system and an "embedded" system?

glen
-- 
{glen e. p. ropella <address@hidden> |  Send lawyers, guns, and money!  }
{Hive Drone, SFI Swarm Project         |            Hail Eris!            }
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