[From Bill Powers (2004.03.29.1607 MST)]
Bill Williams 29 March 2004 4:30 PM CST --
Ok. However, I would like you to consider, while we are fiddling about
picking at nits, the following issue:
On page 280 in the appendix to _B:CP_ in the paragraph that begins "The most
common error ..." In a two sentence paragraph you dispose of the problem
presented by the way almost everyone things about causal relationships.
You say, "Such analyses are almost always qualitative and therefore do not
reveal the quantitative difficulty created by that approach."
The page that follows is suppose to illustrate what this difficulty is --
tha failure to treat time correctly. I don't know how many people actually
read it.
Off hand who among the in the CSG community could take that sentence and,
off the top of their heads, expand the sentence into a four or five page
description of the problem?
Actually, lets not get into an invidious matter of naming names. But, how
about making an estimate of how many persons in CSG understand the problem?
I think just about all the people who do simulations, which is five, maybe
six. The "slowing factor" may be used in a sort of rote way by some, but I
think they all know pretty much why it's needed.
I am making a special point of this issue because I am convinced that it
will be impossible to adaquately explain to ecnomists why your model takes
the form it does in the absence of an explaination of this issue.
You are probably right.
And, in
my experience with economists, and I am considered to be well acquainted
with theoretical issues in economics, I have only encountered five people
who seemed to understand the question. One my my mentor J. Fag Foster. One
might be Sturgeon-- but it is not easy to tell how well he understands the
question-- and it isn't remotely a recomended practice to probe at his
understanding, and I wouldn't dare attempt to do so covertly. And, two have
been my students. But, both of these had extensive preperations -- one took
a math degree at 19, and the other had been an electrical powerplant senior
engineer. Otherwise I have found it enarly impossible to explain the nature
of the problem. Let alone create an awareness of why the problem is
important.
And, in the absence of an understanding the principles upon which you are
attempting to model the economy don't make any sense. So, it seems to me
that either an effort is required to explain this issue better or we content
ourselves with an extremely restricted audience.
All it takes is one well-known person with one foot in each world. I
haven't got into this yet with Bruun. I'm used to working with restricted
audiences!
Perhaps the best way to introduce the model is to show it doing interesting
things. Maybe if we can get it to work realistically (I don't claim that's
true yet), people will begin to ask how we did that. If they demand to be
told, then of course we can be wheedled into parting with the information.
Another approach for students is to use a simulater like Vensim, which is
simple to use and quite a lot of fun. You can download Vensim PLE (Personal
Learning Edition) (Meaning, of course, Vensimple) free, and do a lot with
it. Find it through Google.
With a simulator you can show how dynamic systems work. I think just
modeling a few things like a pendulum or a ballistic missile or a leaky
bucket being filled from a spigot can give an intuitive feel for
time-varying systems, and help to get away from the sequence-of-events
concepts that cause all the problems.
I don't usually worry about how many people will understand what I'm trying
to do. I have enough to do just overcoming my own limitations of time,
persistence, and understanding. Those who are willing to try to get it are
warmly urged to do so.
Best,
Bill P.
Best,
Bill P.