Back to square one?

[From Rick Marken (930412.0900)]

I said:

The fact of the matter is that the input
is not involved in directing the output AT ALL; input is DIRECTED by the
reference signal (via the closed loop). That is, output is neither a


of input nor of input and reference levels together.

Avery Andrews (930412. 1608) replies:

It depends on the time-scales -- if you're analysing things on a time
scale smaller than the transport lag around the loop, then output
is determined (`guided' was a bad choice of word, I think) by input and
reference level jointly. On a larger time scale, the input is
determined by the reference level, just like Rick says.

This was Martin Taylor's point at the start of this discussion. We
found that even the time scale doesn't let you bring the input in as
a cause of the output. The reason is, basically, that THE LOOP IS
ALWAYS THERE, so input is always both a cause AND a result of output.
Only under very special circumstances can o be reconstructed from
the input, i, (or from i and the reference,r); specifically, when
i = o + d. But even in this case (as Bruce Nevin pointed out) the
relationship is just coincidental -- it is not actually the result
of i being turned into o values by the system. When i is a non-linear
function of o there is no relationship between observed values of i
and o. Just as there is no such thing as "impetus" in the Newtonian
model, there is no such thing as "input determination of output" in PCT.

There is quite a lot that everybody does indeed know,

What people "indeed know" may simply be wrong; see above.

and repeating it
over and over again does not assist people in noticing the stuff that
they actually don't know

We are trying to repeat it and demonstrate it in many different ways
so that maybe people will find one of these ways a helpful aid to under-
standing PCT. A willingness to accept the possibility that one does
not "already know" stuff is, I think, a prerequisite to learning PCT.

(like, behavioral scientists who think that
feedback is old hat don't seem to have noticed that they have no
methodology for ascertaining refererence levels, and therefore
have no chance at all figuring out what's going on if what they're
looking at is a hierarchy of control systems).

I don't think behavioral scientists will change their ways until
they see the fundemental difference between their own and the PCT
view of system operation. I don't see why behavioral scientists would
worry about not having a "methodology for ascertaining reference
levels" if they don't WHY not looking for them is a problem. If inputs
are at least SOMEWHAT involved in the determination of behavioral
outputs, then why not keep trying to improve our methods of determining
how inputs do this? Behavioral scientists are unlikely to turn to The
Test until the realize, very clearly, that o is not a function of i.

they agree with
me in seeing `cause' and `effect' as an expository vocabulary which
is sometimes useful in conveying a preliminary sense of what is going

But it's not useful: it's wrong. I am convinced that this cause-effect
"expository vocabulary" has effectively prevented behavioral scientists
from seeing what PCT is all about. It's not about cause and effect;
it's about control.