Guy Hoelzer  wrote:

> pdunkel{at}paleblue.net (Dunk) wrote...
> > On Wed, 18 Dec 2002 01:08:54 +0000 (UTC), wilkins{at}wehi.edu.au (John
> > Wilkins) wrote:
> > 
> > 
> > >To my mind, "emergent" means "I am surprised
by the ways the compnents
> > >of this thing make it behave, because it is too hard to calculate or we
> > >do not know enough yet".
> > 
> > 
> > Incredible!  Someone is at least on the right track!  :) 
> 
> This notion is explicitly excluded from the definition of complexity
> as it is used these days.  The term "complicated" would be used to
> describe such a situation.  When something is complicated, our ability
> to guess about its behavior is constrained by our prior knowledge or
> computational capacity.  "Emergence" specifically refers to phenomena
> that do not exist to ANY degree in the parts of the system.  Rather it
> comes about do to the interactions among the parts and is generally
> scale (number of parts and their densities) dependent.

I'm aware of that, Guy. But the term is equivocal, and enthusiasts often
use it to mean any property, dynamic or phenomena that *cannot*
(logically?) be derived from a full state description of the system, the
interactions between the components, and the external or boundary
conditions of the system. The sorts of properties you are describing
here are trivial. The "fluid" properties of water are not in any way the
statable properties of hydrogen or oxygen atoms and their bonding
capacities. But that does not mean that "fluidity" is somehow a property
over and above the combinatorial properties of the atoms (and the
existence of energy flows, gravitational attraction, and the vessel
shapes, etc).

The so-called "reductionist program" (which does not reduce in the ways
many often say it does, and which is hardly a program in science)
assumes exactly what you state - that by looking at the ways things
interact we can come to a complete explanation of the gross dynamics of
the system. Emergence often means something more than that - dare I say
it, something irreducible to reduction?

This is not to say that we will immediately be able to make the
inferential connections from components to system, or that we won't find
interesting things out along the way (like Kaufmann's N-K "law"). But
"interesting" is still relative to some observer...
> 
> > >JS Mill, in his System of Logic (1842) argued that there were
properties
> > >of water that could not be reduced to the sum of the parts. These days
> > >we can do that on computers. Another fine philosophical
thesis destroyed
> > >by actual science :-)
> 
> But we can't do it with equations because the mean field assumptions
> implemented by the use of parameters ignores the localized temporal
> and spatial events that are critical to the emergent qualities of
> water.  Temporally and spatially explicit computational models can
> avoid some of these critical assumptions.

Hang on; aren't computational models based on equations? I thought some
English fellow showed that everything that is computable (such as
equations) is computable on a UTM...

I'm not sure what the point about parameters is here. In a simulation,
you choose a set of parameters. In the context of, say, the molecular
properties of water solutions in a cell, you set up realistic
conditions.
> 
> > But then there follows a reference to "The "whole"
 is not the same as
> > the "sum" of the parts."  Mill was sensibly referring to
> > predictability, but the expression is too often used in a silly way:
> > both "whole" and "sum" refer to different
ways of combining parts; two
> > different combinations are different - of course. 

Not exactly. Here's what Mill says (calling emergence "heteropathy") in
Bk I, ch. X, sect 4.:

"When the laws of the original agents [the components] cease entirely,
and a phenomenon makes its appearance, which, with reference to those
laws, is quite heterogenous; when, for example, two gaseous substances,
hydrogen and oxygen, on being brought together, throw off their peculiar
properties, and produce the substance called water -- in such cases the
new fact may be subjected to experimental inquiry, like any other
phenomenon; and the elements which are said to compose it may be
considered as the mere agents of its production; the conditions on which
it depends, the facts which make up its cause.

"The _effects_ of the new phenomenon, the _properties_ of water, for
instance, are as easily found by experiment as the effects of any other
cause. But to discover the _cause_ of it, that is, from the particular
conjunction of agents from which it results, is often difficult enough.
In the first place, the origin and actual production of the phenomenon
are frequently inaccessible to our observation. ...

[Water can be made to give off H and O, and H and O can be made to give
water]

"Where two phenomena, between which the laws or properties of which,
considered in themselves, no connection can be traced, are thus
reciprocally cause and effect, each capable in ts turn of being produced
from the other, ... this causation .. is properly transformation. ...

"In these cases, where the heteropathic effect (as we called it in a
former chapter *) is but a transformation of its cause, ... the problem
of finding the cause resolves itself into the far easier one of finding
the effect...

[There follows a philosophy of mind argument not unlike holism. Mill
effectively comes up with supervenience.]

"* Ante, chap. vii, §I."

As I read him, he is saying that it is not a problem of predictability
but of inferring from one domain (the properties of water) to another
(the properties of the components) and vice versa. He is interested in
finding the causes of phenomena than in predicting what will occur in
the future (i.e., in retrodiction). Anyway, the fact that we *can*
simulate the microstructure of water computationally is enough to
undercut the claim that the properties of water are not inferrable from
the properties of the components.
> > 
> > But that's minor.  The giant clinker is "unpredictable in
principle".
> > 
> > What principle?  Who gets to choose the alleged principle?  Who
> > decides when to give up and declare X unpredictable?  This is
> > unpredictability of the gaps.
> 
> I am coming to agree with this point.  After thinking about some of my
> arguments in response to Joe Felsenstein, I think that the
> "unpredictable in principle" issue is a distraction for the same
> reasons you gave.  After all, if the behavior of a complex system can
> be characterized computationally, then isn't it predictable in
> principle given assumptions about the external environment, and so on?
>  While physical emergence is often surprising to us, this just is a
> side effect.

The notion is entirely relative to the computational capabilities of
humans and their tools. Think of it like this:

There are the following sets and subsets, in order of decreasing scope:

The universe
  The computational part of the universe
    The physically computational part of the universe
      The humanly p.c.p.o.t.u 
      (i.e, that which the human race as a whole might compute)
        The societally h.p.c.p.o.t.u
          The individually s.h.p.c.p.o.t.u
            The conveniently i.s.h.p.c.p.o.t.u

Somewhere between the societal and the species level lies "emergence" -
that which we could perhaps calculate but which we are not likely to
because we'd run out of time and resources to do it. But often
"emergent" means something that falls between the individual and the
societal - more than an individual could work out, and less than a
society might, but which hasn't been yet...
> 
> > Much of the above discussion is,... um.. well here is an example: 
> > Question - Are the properties of water predictable from the properties
> > of the elements?  [ Could be any compound ]  
> > The answer is No but Yes is given -- but it is clear that the Yes is
> > not based on properties but on a theory aka principle [ QM in this
> > case].  

For some definitions of "properties", the answer is definitely yes. I
don't have the files on my hard disk right now, but I have read papers
on the microstructure of water is simulable. I think you mean that the
properties of a *specific* piece of water (e.g., the exact hydrodynamic
turbulence) might not be, because the outcome is due to imponderable
properties at the QM level.
> 
> I agree.
> 
> [snip]
> 
> > In any case prediction depends on theories not properties hence the
> > discussion of predictability from properties is off target.  This
> > accounts for some of the confusion.    
> 
> Good point.
> 
> > "Unpredictable in theory" obviously depends on the
theory, and at best
> > gives us emergence based on gaps in present understanding. 
> > This makes emergence a property of our limitations.  You can't be sure
> > that something cannot be predicted from *some* theory.  
> 
> It is not at all about predictability in any context.  It is about the
> development/evolution of scale and context specific phenomena
> instantiated by interactions among agents (parts once the larger scale
> phenomenon has emerged).
> 
> > Now what if someone wanted to get practical?   Once you see that 
> > "unpredictable in principle" doesn't mean anything much and only
> > creates confusion, it's easy: 
> > 
> > Emergence is the flip side of reduction.  If complicated phenomena can
> > be "reduced" i.e. explained from simple rules, then
complexity can
> > emerge from simple rules aka laws aka theories. 
> 
> Emergent phenomena cannot generally be explained from simple rules
> alone at smaller scales alone because they are scale and context
> dependent.  If you define the scale and environmental context of the
> system, then recognize the behavioral and interaction rules of the
> parts, you can "explain" an instance of an emergent phenomenon.  It is
> also of great interest to determine the "generic" tendencies of kinds
> of systems.  Complexity theory will ultimately have a deep and lasting
> impact if enough relevant "universality classes" can be determined.

This boundary conditions objection of your strikes me as odd, Guy. Of
course things are scale dependent - some phenomena re simply
unrecognisable at too small a scale. But this is a mtater of observer
focus, that's all. Or am I missing the point?

This is getting more off topic, so perhaps I should bring it back a bit.
For me, evolution is not emergent in the "metaphysical" sense that there
are properties at higher levels of inclusiveness (say at the species
level) that are not due to the properties of the components and their
relationships to each other, together with the inital and boundary
conditions of the system being considered. But things are emergent for
the biologist, who can neither observe all these conditions nor measure
with sufficient exactness those that can be observed. We cannot predict
the course of evolution for obvious reasons, but that is a limitation
more on ourselves than a fact about the things observed here.
> 
> Cheers,
> 
> Guy
Here's a paper on the philosophical issues that might be useful.

Hüttemann, Andreas, and Orestis Terzidis. 2000. Emergence in physics.
International Studies in the Philosophy of Science 14 (3):267-281.
-- 
John Wilkins
"Listen to your heart, not the voices in your head" - Marge Simpson
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