[Hans Blom, 960912]
(Bill Powers (960911.1320 MDT))
What do you mean by a "variable which exists outside the sensors,
in the environment"? If such a thing existed, how could we access
it, except as a measurement through some kind of sensor?
I was taking the engineer's point of view, from which both the
signal and the thing it stands for can be seen. Consider the
variable we call relative humidity. This variable can be represented
by a signal, but there is no single measurable thing in the
environment corresponding to the signal.
All right, I see what you mean, I think. If both the "signal" and
"the thing it stands for" can be perceived (i.e. measured through
sensors), we can relate (or correlate) these measurements and extract
invariants. We cannot (cor)relate an observable and an unobservable,
regrettably. We cannot know (about) the world but through our
sensors. It's all perception...
In MCT, the notion "relative humidity" -- as any other notion --
would be a notion _of the model_, not something with an independent
existence in the environment. In MCT, there is no need for such a
thing as an external reality (although in simulations we may posit
one, because we need a generator of the measurements). What is known
of the environment is only the measurements, the outputs of the
sensors. Nothing else. If more is "known", it is _relations_ that the
model has somehow been able to extract out of those measurements. So,
in a sense, the model takes the "engineering point of view" in that
it imposes some kind of order on the measurements -- in the form of
certain relationships, not between the measurements per se (although
this can be done) but between "idealizations" (model states). Simple
models with only a few degrees of freedom (tunable parameters) can
only discover limited order, more complex many-degrees-of-freedom
models may be able to discover more (parametrize more fully).
If a priori knowledge is used, it is NOT about the environment (of
which we know nothing except through the measurements) but about how
extracted order can best be represented. However, we humans tend to
equate/confuse our expertise of how to do this well with knowledge of
the "real" world. This desire to "extract meaning" seems to be a
hard-wired human property, of which we should be aware.
In daily life as well as in science, the confusion between (unknown)
world and (known) model can create havoc, when e.g. the same
relationships are parametrized differently. In science, we would call
this having different theories which yet cover the same domain. One
person describes a point, for instance, in terms of its x- and y-
coordinates, someone else in terms of radius and angle. The question
who is "right" and who is "wrong" is useless; it is just a different
parametrization. What is important is to come to understand the two
theories or "languages" and to provide for a translation. And, maybe,
that one parametrization may sometimes be more suitable than another
-- while for a different class of problems a different
parametrization will more easily lead to a solution / be a better
tool for control. This may be the reason why I am not disdainful
about people who have multiple (seemingly) conflicting theories ;-).
I have no idea what a "perception of beforeness" would be.
When you go through a door, do you walk through it before you open
it, or open it before you walk through it? Can you tell the
difference? If so, you can perceive the temporal relationship
"before" as in "open _before_ walking through."
I can adequately go through a door, thank you. But I'm not aware that
I need a perception of "beforeness" in order to be able to do so.
Maybe my model parametrizes differently from yours ;-).
I don't believe in such abstract notions, I'm afraid ...
They may not fit your intellectual schemes, but if you can't
perceive beforeness you are going to have a lot of practical
difficulties.
Can we translate someone's "intellictual schemes" with that person's
way of ordering the world? Would a cat have a notion of "beforeness"?
A flea? A bacterium? A virus? They can all adequately handle the
before-after relations that are important to them, yet I doubt
somehow that all these species have the intellectual ability -- or
the need -- to develop a "beforeness" concept. It may be a notion in
_your_ model, it need not be one in mine.
Greetings,
Hans