I have been away for a week but, ....
I think I had better make clear (or elaborate) on the relation
between my use/definition of "complexity" and Rosen's.
Rosen's use of "complexity" is a special case of mine where the
"difficulty" involved is the utlimate difficulty of impossiblity.
Thus, in this case, the definition specialises to:
"That property of a language expression which makes it
*impossible* to formulate its overall behaviour completely, even
when given almost complete information about its atomic
components and their inter-relations.".
Thus if the "difficulty of overall speicifcation of behaviour" you
are concerned with is that associated with the limits of the
classical reductionist/Newtonian method this would be the
approapriate interpretation of my general definition in your
domain (though I think Newton homself mught be somewhat
annoyed by this use of his name - he was very aware of the
limitations of his knowledge). This is fine and good, knowledge
always gains from a variety of approaches however successful
any one is in its own domain, so that pointing out the limitations
of established methods and looking for other ways is to be
applauded (but judged by its ultimate utility).
I find it somewhat strange that this should be considered the
_only_ use of the term "complexity" though. Surely much of the
power and utility of language comes from the fact that words
can be used from many perspectives and for many uses while
retaining the same "flavour" (and I am *not* going to define
that!). Most of the world (maybe SFI and anti-reductionists
apart) will frequently use terms like "X is more complex than Y,
which is more complex than Z". To insist that the rest of the
world should change their language to suite the reductionist
debate seems topsy-turvy!
This is not to say that the distinction intended by such as Don, to
indicate a crucial difference between what they call
"complicated" and what they call "complex" is not a useful one.
But that these specific meanings of these terms are a strictly
"local" usage. As long as everybody knows what the others are
talking about and can use language to fruitfully discuss the
intended distinctions this is all that is required. The rest is
politics!
I will now set out the *personal* reasons _I_ use complexity as I
do:
1. I am interested in identifying the core of the cluster of
concepts which have been used under the term "complexity".
2. I think that analysing "complexity" in a particular way (as I
defined it) reveals something useful about the sharper
(analytic?) application of the concept, so that confusions of the
type we are discussion are clearly delineated and thus avioded
but so that its wide range of applicability is still retained.
3. I want to be able to talk about comparing complexity, this is
in fact the most common use of this term! Thus Rosen's
approach is too specific to meet all my analytic needs.
4. I want to be able to talk about and investigate the *roots* (I
don't say "causes") of the type of complexity that Rosen
identifies. Imagine a long evolution from systems that are
somehow "simple" (a mere mixture of chemicals) to something
"complex" i.e. us (given some uniform method of reprentation,
of course)! Limiting the meaning of "complexity" to a particular
paridgmatic one like Rosen's means that somehow in this
evolutionary process it suddenly swaps from state "simple" to
state "complex" and does this (essentially) only ONCE. This is
very unhelpful if you are trying to use a concept such as
"complexity" to understand such an emergence
_as_a_process_.
5. Keeping the term as close as possible to common usage
while *refining* it (not restricitng it) to reveal more of the
assumptions and chaacteristics of its use.
I am, of course, pesimistic about its success for many reasons:
An Vranx outlined the power such terms gain as naratives as
they move into the public domain; the *status* that the term
"complexity" conveys to an academic enterprise - which means
that deliiniations of its use is somewhat political (see recent
Sci.Am. article for an example); the ease with which the
ingrained habits/world-view of each group of humans is
extended (by that group) to the whole world (e.g. try discussing
the merits of your favourite editor/WP with someone else!); and,
of course, the sheer glorious perversity, imagination,
individuality and diversity of our species.
In the end, all I am concerned with is identifying some useful
core of the various uses of the term "complexity" and looking at
it in such a way as to make clear some of the assumtions and
relativities in its use and thus reduce some of the confusion
surrounding it.
----------------------------------------------------------
Bruce Edmonds
Centre for Policy Modelling,
Manchester Metropolitan University, Aytoun Building,
Aytoun Street, Manchester M1 3GH. UK.
e-mail b.edmonds@mmu.ac.uk
Tel no. +44 161 247 6479 Fax no +44 161 247 6802
WWW. http://bruce.edmonds.name/bme_home.html