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Re: meanings of model



Howard, could you enlarge on this statement, please:
 
I am a Constructivist, so I would phrase your question conversely: when do the limits of physical laws impinge on the capacity of formal symbols to
have meaning? That is, when do the purely syntactic expressions of formal
mathematics go beyond what can be measured or encoded by nature?
 
It makes sense to me that "purely syntactic" expressions of formal mathematics move into realms which do not exist in nature (like "transfinites," or different "sizes" of infinities, for example). Since natural systems are bound by contextual constraints, any purely syntactical mode of modeling is not always going to be "congruent". Context is equivalent to "semantics". In other words, there is meaning/information in the relations created by context. So when mathematics is bound by the semantics of mathematics it's not a problem-- it's only when science tries to say that nature is like mathematics that it becomes a problem. ("We must never forget that number theory is about numbers.") I don't think we are in any disagreement on this.
 
My main area of concern is your phrasing; "the limits of physical laws". Do you mean physics-based laws? Or do you mean what my father referred to as "Natural Law" (meaning whatever consistencies are involved in generating/constraining the universe, whether we know about these consistencies or not)?
 
Another area of concern is the phrasing; "what can be measured or encoded by nature". I doubt that even my father would say he could tell you the limits of what nature can or cannot do. He could only generalize and say that natural systems cannot behave in ways inconsistent with Natural Law. Science in general is way behind; a small subset of all there is. Science has deliberately limited itself by adopting the machine metaphor which is the same as using a machine to model nature and forgetting that it's a model. So now they are trying to make nature into a system that "realizes" their model and only the evidence which seems to fit is allowed to be called "scientific".
 
The fact that natural systems are capable of "measuring" and "encoding" is not disputed, however. Even people who refuse to believe that living systems are "anticipatory" in the Rosennean sense could not dispute that natural systems are capable of measuring and encoding. On the other hand, just because WE are natural systems which measure and encode, that doesn't mean we do it well or accurately in any terms but our own. In other words, our choices of what to measure and how to measure (in terms of what and how other natural systems are measuring) may not reflect much useful reality according to those natural systems. Their modes of measurement and encoding may be beyond our ability to perceive, much less quantify or qualify. So how can we say what can be measured or encoded by nature? To do so would require that we measure their ability!
 
Judith

----- Original Message -----
To: ***
Sent: Monday, December 13, 2004 2:16 AM
Subject: Re: [ROSEN] meanings of model

At 08:09 AM 12/12/04 -0500, Tim wrote:

>Another way to say it would be: when do the inherent limits of _expression_ in
>formal models (in your first sense) impinge on the capacity for them to be
>formal models (in your second sense)?

HP: There are at least two schools of thought (or two ontologies) that bear
directly on  the form of your question. At the extremes there are the
Platonists who see physical laws as derivatives of abstract forms. "In the
beginning was the word" (John 1;1). And  there are the Constructivists who
see the semantics of formal symbols  limited by physical laws. "Words grew
out of the womb of matter" (Laotzu, Tao Teh Ching 1).

I am a Constructivist, so I would phrase your question conversely: when do
the limits of physical laws impinge on the capacity of formal symbols to
have meaning? That is, when do the purely syntactic expressions of formal
mathematics go beyond what can be measured or encoded by nature?

Also Constructivists, like most computer modelers, see no reason why the
formal concept of Turing computability should limit how we actually write
programs. Many programs for physical and biological models are not even
algorithms because they do not halt by themselves. In fact, strictly
speaking, our computers are not Turing-equivalent. They are finite memory
and finite state machines, and all theorems on computability depend on the
syntax of infinite sets.

This is a classical metaphysical controversy. Henri Poincare (the
constructivist) and Bertrand Russell (the formalist) argued this for years
and finally agreed to disagree. Rosen and I were closer to agreement than
Poincare and Russell, but there was no doubt Rosen was not as
constructivist as I am. We will not resolve this issue here, but I think
understanding why there is an issue might help the discussion.

Poincare's basic argument is that there is no empirical, ontological, or
semantic evidence for infinite sets and certainly none for transfinite
sets. He saw infinite sets as useful but purely syntactical games with
symbols. He saw Richard's and Russells's paradoxes (and would have seen
Goedel's and Turing's theorems) as just limits on how you can play
syntactic games, but semantically irrelevant for models of physical reality.

Of course, the constructivist agrees that there are formal symbolic models
(in my first, right-hand sense) that he cannot compute by Goedelian
conditions; but to convince a constructivist that this is scientifically
relevant requires an example of physically observable behavior that he
cannot adequately model (in my holistic second sense) by satisfying only
the Hertzian conditions.

Howard