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

[Barry McMullin]

[I've been studiously avoiding this thread because (a) I haven't time for
frivolous enjoyment right now (;-), and (b) it's all my fault anyway because
I pointed Glen at the damned "Life Itself" book in the first place ...
but, at the risk of ignoring all the carefully established context, I'm
going to jump right in and take issue with Glen on one point - either
a minor niggle, or the very crux of Life, The Universe and Everything,
depending on your viewpoint...]

glen e. p. ropella wrote:
> When *I* talk about Alife, however, I usually intend to focus simply
> on "iterated systems."  This is, I think, a little more broad than
> what Rosen would consider.  The fundamental criterion for membership
> in this set is that a system must be iterated in order to make useful
> statements about it.  I.e. we have a big bag of "stuff" (could be
> particles, could be patterns of interaction, etc) whose behavior we
> can't predict; so we iterate it either forward in time or via some
> other successive operator.  Then we take measurements on it and try to
> extract information from it.

I am *not* going to argue about how to "define" the word "ALife" 
(phew!).  

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.

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.

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

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

Cheers,

- Barry.

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...


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