Re: Modeling the Emergence of Political Parties

[glen e. p. ropella]

At 09:54 AM 10/22/99 -0500, you wrote:
> I think I am using the term result in a different sense than you are. Of
> course, there are technical procedures to create and evaluate
> simulations.  It it is technically possible to tell if two sets of runs
> are significantly different, or if one distribution causes a set of
> outcomes different from another.

If you expand this to say that any two data sets can be
compared, then your talking about validation.  Right.

> I think the clearest, easiest to justify simulation result is obtained
> like this. SOmebody writes a book using informal tools or differential
> equations to make some claim that something is likely to happen.  That
> gives you a nice null hypothesis, and you can then build a simulation
> according to their story, and see what happens. If it does not match
> their prediction, you have a great result. If it does match their
> prediction, people might not be very interested, but it could still be
> useful.

Well, if the simulation *doesn't* match their hypothesis, you
still may not have a great result because there could easily
be a verification problem... the sim may not do what you think
it does.  And if it does match their hypothesis, then obviously
you may not have a result.

>   The key is that, whether or not you have a result depends on
> the research community, their questions, claims, and your ability to
> participate in their argument.
>
> So, unless I misunderstand your comment, I still don't think I'm far
> from the truth.

No, you're not at all far from the truth.  I really just wanted
to caution you about criticizing simulation in ways that
could be misunderstood.

And, I freely admit that, since all of science, mathematics,
simulation, ... indeed most everything we do relies in
fundamental ways on the community in which we do it.  That's
what makes us a social system.

However, you're slipping into a more profound argument when you
mention things like "theorems", "math", "methodology", and
"internal validity".  Steve has it right that a) validation
(the comparison between a simulation and the ... ahem...
real world) is the same as verification (the comparison between
an implementation and a formal model -- e.g. ObjC and some
set of equations), b) a mathematical (or any kind of formal)
model is just as constrained, if not more, as a simulation --
hence all the arguments about what some given set of maths
*means* in fields like physics, and c) there seems to be
some *urge* to attribute more meaning to formal models than
to ad-hoc models.  (Of course, I'm reading Steve's email
with my own prejudices...he may not have intended to say
anything like that at all. [grin])

The ultimate test, of course, of whether you've got a
"result" is if your simulation says something about the
science around it.  In fact, simulations are almost always
messed up in some way or another, where sometimes the
modeler is aware of the artifact and sometimes she's not.
The important thing is that simulation is a good scientific
tool in that bad simulations (those that create cognitive
dissonance -- re: Donaldson's email signatures) are often
as, if not more, helpful than good simulations, because they
help you refine your formal model.

So, what I'm getting at, here, which mirrors Steve's comments,
I think, is that simulation doesn't produce results at all.
It's just a part of the thought process.  A researcher uses
pencils and she uses simulations.  A researcher uses first-order
logic and she uses simulations.  A researcher drives a car and
she uses simulations.  A researcher digs in the dirt looking
for insects trapped in amber.... and a researcher uses
simulations.

Heh, which brings me to the interesting point of saying
that simulation is just Yet Another Tool in our little bag
of artifacts we use, nothing more, nothing less.  What
I want to avoid is having people wandering around talking
about simulation the way they talk about the slide rule or
their VCR.  It may not be easy to program your VCR; but,
it's not a black art, either.

glen



--
glen e. p. ropella =><= Feeding the hamster wheel.  Hail Eris!
Home: http://www.trail.com/~gepr                (505) 424-0448
Work: http://www.swarm.com                      (505) 995-0818


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