It is the cause, my soul.

[Tom_BOURBON3]

Tom Bourbon [950110.1723]

[From Rick Marken (950110.1030)]

Martin Taylor (950109 17:30) --

Nothing in this world is "a cause of itself" if you include the time
dimension.

Then, by the same argument, nothing in the world is a cause of anything else.

That is the *appearance*, if not the intent, of what Martin said. Martin?

You say:

It [the perceptual signal] is part of the cause ofthe perceptual signal at
time t+tau, where tau is definitively non-zero, and at later times, possibly
extending beyond limit.

But this is true of all variables in the loop:

p --> e --> o -->q -->p

The error signal, e, is caused by p (and the reference signal,r) but at some
(very small) time delay; output, o is caused by p at some (longer) time
delay; same for the environmental variable, q and, finally, p itself. So, if
you don't want to say that p is a cause of itself in this loop because of the
time delay between p as cause and p as effect of that cause then you would
also have to say that p is not a cause of q, o and e either, since there is a
tine delay between cause and effect with all these variables.

Rick, you are taking the words out of my mouth. Is that sanitary?

Of course, even Rick's graphic presentation depends on laying all of the
variables out as though they worked in a lineal fashion. In a closed loop,
causality does work in one direction, but it does not work in a lineal
manner, something Rick makes clearer below.

So the "opposite" of a straight line should be seen as a helix, not a circle.

If you want to capture the time dimension, I suppose this is true. But a
helix can also be a way of preserving the (incorrect) intuitions of a
sequential analysis of a control loop; p THEN e THEN o THEN q THEN p again.
In fact, all variables in the loop (except the disturbance and reference
variables, which are not actually in the loop) are always (and
simultaneously) a cause and an effect of the other variables in the loop. A
helix gives the impression that the value of p as CAUSE differs from the
value of p as EFFECT. This provides a way to sneak a cause-effect view of
control back into the picture; p causes output and then waits until the
output changes p so that a new output can be caused. This is NOT the way a
control loop works. At any instant, the value of p is BOTH a cause (of future
values of p) AND an effect (of previous values of p).

Now you are taking the words right out of my keyboard. Definitely
unsanitary, Rick!

Only slightly more seriously, Martin, when I read your post I was
immediately struck by the idea that you were trying to preserve lineal
causality and hide the fact by invoking the image of a helix. Event would
follow event, in lockstep, along the straight line that has been bent into
a helix. I doubt that was your intent, Martin, but that was the appearance.
All functions in the loop act all of the time. All signals are present all
of the time. Except for the few milliseconds after a big impulse
disturbance hits an environmental variable that is controlled by the system,
there are no times when you can trace a big impluse-like "event" through
the system, the way you can follow a small rodent through a big snake.

Are Rick and I missing something in your analogy, Martin?

Later,

Tom

[_Martin_Taylor]

[Martin Taylor 950110 17:30]

Rick Marken (950110.1030)

Nothing in this world is "a cause of itself" if you include the time
dimension.

Then, by the same argument, nothing in the world is a cause of anything else.

Add "that is occurring at that precise moment" then of course that's true
(if you believe in the speed of light as a limiting signal velocity). Things
that occur in one place at one time can affect only things that happen later
at any other place. As for "cause," that's a whole 'nother philoshical
discussion.

It [the perceptual signal] is part of the cause of the perceptual signal at
time t+tau, where tau is definitively non-zero, and at later times, possibly
extending beyond limit.

But this is true of all variables in the loop:

p --> e --> o -->q -->p

Yep.

The error signal, e, is caused by p (and the reference signal,r) but at some
(very small) time delay; output, o is caused by p at some (longer) time
delay; same for the environmental variable, q and, finally, p itself.

I persist in maintaining that you are making a labelling error. "p itself"
is not the same "p" as mentioned in the first part of the sentence. There
is a place at which signal values can be measured, and you can call this
place "the perceptual signal p" if you want. But it's misleading to
use this wording if you also want to use the words "the perceptual signal"
to refer to the VALUE of the measurement made at the PLACE at a particular
TIME.

You can talk about "the perceptual signal" also to refer to a time function
that describes the entire set of measurements that might be made between
times t and t1. If t1-t is long compared to the loop delay, then perhaps
it would be correct to say that p is a partial cause of itself. Portions
of the time function affect other (possibly overlapping) portions of the
same time function.

But a
helix can also be a way of preserving the (incorrect) intuitions of a
sequential analysis of a control loop; p THEN e THEN o THEN q THEN p again.

It could be, but it need not be. I guess that if you want a good analogy,
it's hard to produce a visual one, but a helix that starts at some point and
smears itself out ever more widely as it winds around a cylinder would be
better than a simple helix. At least such a visual metaphor wouldn't lend
itself to the misinterpretation that worries you. But analogies often
(always?) lead to misinterpretation if they are taken to too fine a level
of detail. They shouldn't be taken as more than a cue or clue to a way
of looking at the real thing.

At any instant, the value of p is BOTH a cause (of future
values of p) AND an effect (of previous values of p).

Yep. In the helix analogy, the PLACE "the perceptual signal" would be
represented by a line parallel to the axis of the helix, which makes clear
this point. The "smeared helix" shows how this past-future effect isn't
a matter of a series of causal impulses, which is what you complain about.

I think your vision of a control loop as a helix might be keeping you from
seeing that there is no way that the perceptual signal can "inform" a control
system about what to do to control that signal.

No, that's a quite independent issue. I think it is your visual analogy
for what "information" means that prevents you from seeing this, and from
using your skills to take advantage of it. Since I can't derive your model
of "information" from your postings, I can't do much to help.

Isn't it time to just admit that information theory is the wrong model of
living organisms (and the wrong tool to use to study them).

Never was a model. May or may not be a helpful tool, but it can't be a
"wrong" tool. Like any tool, it can be wrongly used, and can cause damage
if wrongly used. I'm not pushing it on CSG-L, because it seems too hard
to get the basics accepted for what they are, and it's not (at present)
worth my putting much effort into another attempt. If and when I manage
to make some testable predictions, I'll let you know. At present I'm
doing other things.

But it has nothing to do with cause-effect thinking. At least, I don't see
the connection.

Martin