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I finally have some time to type in the other part of my father's
discussion about anticipatory vs reactive control mechanisms in modeling natural
systems:
From Page 9 of Anticipatory Systems:
"I was astonished to find this profusion of anticipatory
behavior at all levels of biological organization. It is important here to
understand why I found the situation astonishing, for it bears on the
developments to be reported subsequently, and raises some crucial
epistemological issues.
We have already seen, in the few examples presented above,
that an anticipatory behavior is one in which a change of state in the present
occurs as a function of some predicted future state, and that the agency through
which the prediction is made must be, in the broadest sense, a model. I have
also indicated that obvious examples of anticipatory behavior abound in the
biosphere at all levels of organization, and that much (if not most) conscious
human behavior is also of this character. It is further true that organic
behaviors at all of these levels have been the subject of incessant scrutiny and
theoretical attention for a long time. It might then be expected that such
behavior would be well understood, and that there would indeed by an extensive
body of theory and of practical experience which could be immediately applied to
the problems of forecasting and policy-making which dominated the Center's
(Center for the Study of Democratic Institutions) interests. But in fact,
nothing could be further from the truth. The surprise was not primarily that
there was no such body of theory and experience, but rather that almost no
systematic efforts had been made in these directions; and moreover, almost no
one recognized that such an effort was urgently required. In retrospect, the
most surprising thing to me was that I myself had not previously recognized such
a need, despite my overt concerns with modeling as a fundamental scientific
activity, and despite my explicit involvement with biological behavior extending
over many years. Indeed, I might never have recognized this need, had it not
been for the fortuitous chain of circumstances I have described above, which led
me to think seriously about apparently alien problems of policy-making in a
democratic society. Such are the powers of compartmentalization in the human
mind.
In fact, the actual situation is somewhat worse than this. At
its deepest level, the failure to recognize and understand the nature of
anticipatory behavior has not simply been an oversight, but is the necessary
consequence of the entire thrust of theoretical science since earliest times.
For the basic cornerstone on which our entire scientific enterprise rests is the
belief that events are not arbitrary, but obey definite laws which can be
discovered. The search for such laws is an _expression_ of our faith in causality.
[Note from Judith: This was something my father believed also,
it's just that he believed the natural laws were not adequately figured out by
science, as yet.] Above all, the development of theoretical physics, from
Newton and Maxwell through the present, represents simultaneously the deepest
_expression_ and the most persuasive vindication of this faith. Even in quantum
mechanics, where the discovery to the Uncertainty Principle of Heisenberg
precipitated a deep re-appraisal of causality, there is no abandonment of the
notion that microphysical events obey definite laws; the only real novelty is
that the quantum laws describe the statistics of classes of events rather than
individual elements of such classes.
The temporal laws of physics all take the form of differential
equations, in which the rate of change of a physical quantity at any instant is
expressed as a definite function of the values of other physical quantities at
that instant. Thus, from a knowledge of the values of all the relevant
quantities at some initial the values of those quantities at the succeeding
instant are determined. By iterating this process through an integration
operation, the values of these quantities, and hence the entire behavior of the
system under consideration, may be determined for all time. Carrying this
picture to its logical conclusion, Laplace could say "An intelligence
knowing, at a given instant of time, all forces acting in nature, as well as the
momentary position of all things of which the universe consists, would be able
to comprehend the motions of the largest bodies of the world as well as the
lightest atoms in one single formula... To him nothing would be uncertain; both
past and future would be present in his eyes."
This picture of causality and law, arising initially in
physics, has been repeatedly generalized, modified, and extended over the years,
but the basic pattern remains identifiable throughout. And one fundamental
feature of this picture has remained entirely intact; indeed itself elevated to
the status of a natural law. That feature is the following; in any law
governing a natural system, it is forbidden to allow present change of state to
depend upon future states. Past states perhaps, in systems with "memory";
present state certainly; but never future states. It is perfectly clear from the
above discussion why such a commandment is natural, and why its violation would
appear tantamount to a denial of causality in the natural world.
A denial of causality thus appears as an attack on the
ultimate basis on which science itself rests. This is also the reason why
arguments from final cause have been excluded from science. In the Aristotelian
explanation of system behavior in terms of final causes is the province of
teleology. As we shall see abundantly, the concept of an anticipatory system has
nothing much to do with teleology. Nevertheless, the imperative to avoid even
the remotest appearance of telic explanation in science is so strong that all
modes of system analysis conventionally exclude the possibility of anticipatory
behavior from the very outset.
And yet, let us consider the behavior of a system which
contains a predictive model, and which can utilize the predictions of its model
to modify its present behavior. Let us suppose further that the model is a
"good" model; that its predictions approximate future events with a sufficiently
high degree of accuracy. It is clear that such a system will behave as if it
were a true anticipatory system; i.e. a system in which present change of state
does depend on future states. In the deepest sense, it is evident that this kind
of system will not in fact violate our notions of causality in any way, nor need
it involve any kind of teleology. But since we explicitly forbid present change
of state to depend on future states, we will be driven to understand the
behavior of such a system in a purely reactive mode; i.e. one in which present
change of state depends only on present and past states.
This is indeed what has happened in attempting to come to
grips theoretically and practically with biological behavior. Without exception
(in my experience), all models and theories of biological systems are reactive
in the above sense. As such we have seen that they necessarily exclude all
possibility of dealing directly with the properties of anticipatory behavior of
the type we have been discussing.
How is it, then, that the ubiquity of anticipatory behaviors
in biology could have been overlooked for so long? Should it not have been
evident that the "reactive paradigm", as we many call it, was grossly deficient
in dealing with systems of this kind? To this question there are two answers.
The first is that many scientists and philosophers have indeed repeatedly
suggested that something fundamental may be missing if we adopt a purely
reactive paradigm for consideration of biological phenomena. Unfortunately,
these authors have generally been able only imperfectly to articulate their
perception, couching it in terms as "will", "Geist," "elan," "entelechy," and
others. This has made it easy to dismiss them as mystical, vitalistic,
anthropomorphic, idealistic, or with similar unsavory epithets, and to confound
them with teleology.
The other answer lies in the fact that the reactive paradigm
is universal, in the following important sense: Given any mode of system
behavior which can be described sufficiently accurately, regardless of the
manner in which it is generated, there is a purely reactive system which
exhibits precisely this behavior. In other words, any system behavior can be
simulated by a purely reactive system. It thus might appear that this
universality makes the reactive paradigm completely adequate for all scientific
explanations, but this does not follow, and in fact is not the case. For
instance, the Ptolemaic epicycles that are also universal, in the sense that any
planetary trajectory can be represented in terms of a sufficiently extensive
family of them. The reason that the Copernican scheme was considered superior to
the Ptolemaic lies not in the existence of trajectories which cannot be
represented by the epicycles, but arises entirely from considerations of
parsimony, as embodied for instance in Occam's Razor. The universality of the
epicycles is regarded as an extraneous mathematical artifact irrelevant to the
underlying physical situation, and it is for this reason that a representation
of trajectories in terms of them can only be regarded as a simulation, and not
as an explanation."
I'm going to take a break and type the next part in later this morning-- it
turns out to be a bit longer than I thought.Time for coffee...
Judith
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