[From Dag Forssell (2009.04.17.1730 PDT)]
[From Bill Powers
Sorry, it wasn’t Boltzman who said variety absorbs variety. It was
More on Cybernetics, Stafford Beer and Ashby.
I am working on the publication of letters between Phil Runkel and Bill
Powers. Much background information needs to be in place before I release
One of the items is the newsletter Continuing the Conversation, CC,
edited by CSG archivist and dedicated PCTer Greg Williams from 1985
through 1991, when he switched to Closed Loop. Bill and Phil discuss a
few issues of CC in their correspondence, so I want to provide a link to
that which they discuss.
Greg scanned and I recreated the entire series. (Yes, it took many
manweeks). Just today, I have arrived at a point of agreement from
contributors so I can release the pdf file with this series. (You can
search for Beer and Ashby to see what they have to say and what Bill and
Mary have to say to and about them.)
ftp.pctresources.com user name: pctstudent password
Also, I posted the following three times: April 9, 10, and 12, but it did
not appear. We shall see if this message gets posted. I posted and am
posting with the same address I have used many times.
Subject: Re: CSGnet mail archive
[From Dag Forssell (2009 0409 15:40 PST)
Thinking some more about your puzzlement.
Word 2008 for Mac “says the file uses a type that is not
permitted…” The key here is type, or font. I can see that.
Back in the 90’s fonts were bitmapped, unless you went for very expensive
Type 1 PostScript fonts. (Mac did). This old Word file specifies Courier,
a bitmapped font. Now bitmap fonts are ancient history and your program
no doubt substitutes a True Type or even more up-to-date font type, still
a version of Courier, with mathematically defined outlines.
The Word document specifies Courier, a monospace font. Monospace, where
each letter occupies the same width, is required for ASCII images to
So a font and thus document conversion is a given. I can imagine this
being the reason for the requirement to open the document from the Menu.
They are just what I wanted, but there seems to be something a little
strange about the file type. I downloaded the Word package that starts in
1990. When I try to open the files in Word 2008 (Mac), it says that the
file uses a type that is not permitted for opening by double-clicking or
drag-and-drop, but that if I am sure it is safe, I can open it from the
File menu in Word (which I can). The files I have sampled look just fine
when I do that, and thank you very much. I just wonder why I get that
message with what looks like a very ordinary Word .doc
[From Bill Powers
At 09:45 PM 4/17/2009 +0200, Arthur Dykstra wrote:
AD: Dear Bill,
With great interest I am trying to catch up on these interesting
Can you please elaborate a bit more on what you say about cybernetics and
Ashby in the following part:
BP earlier:I saw this happen in
cybernetics, with Ashby’s “Law of Requisite
BP: I assume this is the passage that caught your eye. I was referring to
the concept of requisite variety as a kind of measure of variability,
which is related to uncertainty and the concept of information. Ashby
maintained that the actions of a control system had to have at least as
much “variety” as the environment to be controlled.
For the save of PCTers not acquainted with this law, here is a bit from
The Law of Requisite Variety
If a system is to be stable the number of states of its control mechanism
must be greater than or equal to the number of states in the system being
controlled. Ashby states the Law as “only variety can destroy
variety”. He sees this as aiding the study of problems in biology
and a “wealth of possible applications” . He sees his approach
as introductory to Shannon Information Theory (1948) which deals with the
case of “incessant fluctuations” or noise. The Requisite
Variety condition can be seen as a simple statement of a necessary
dynamic equilibrium condition in information theory terms c.f. Newton’s
third law, Le Chatelier’s principle.
Later, in 1970, Conant working with Ashby produced the Good Regulator
theorem  which required autonomous systems to acquire an internal
model of their environment to persist and achieve stability or dynamic
The idea in that last unfortunate paragraph has steered lots of people
into a blind alley.
While the law of requisite variety may in fact be true (I wouldn’t know),
it’s not sufficient for designing a stable control system, or even a
control system that controls. All it really says is that the control
system must have the same number of output degrees of freedom as the
environment to be controlled. It doesn’t even say they have to be the
same degrees of freedom! If the outputs of the control system can apply
forces to an object’s position in x, y, and z, and the environment
controlled can vary in angles rho, theta, and tau, the number of degrees
of freedom of the output is the same as the number of degrees of freedom
of the environment, but nothing in the environment will be controlled.
Ashby referred to matching the number of “states,” but that
means only that each output variable must have at least the same number
of discriminable states or magnitudes as the corresponding environmental
variable. It still doesn’t say the variables have to correspond in any
particular way. If you match only the number of states, the chances of
creating even a closed loop are pretty small.
Even if all those conditions are met, you still don’t have a control
system, much less a stable one. To have a control system, you need to
give it the ability to sense the state of the environment in each
independent dimension (a subject Ashby totally ignored, apparently), to
compare what is sensed with a reference condition, and to generate an
output that affects the same variable that is sensed in such a way
that the difference between the sensory signal and the reference
magnitude is minimized and kept small despite unpredictable disturbances
of the environment. The law of requisite variety says nothing helpful
about those fundamental requirements. It’s one of those generalizations
that, while quite possibly true, is useless for designing or
In “Design for a Brain” Ashby abandoned the best approach to
control theory and switched to a very bad version in which the variables
are discrete and enumerable. I think this is what gave rise to the
current fad called “modern control theory,” and that the
underlying principle he and his followers adopted is completely
impractical as a model of living systems (or the systems they control).
Ashby thought you could design a system so it would compute how much
action and what kind of action were needed to produce a desired result,
and then execute the action and get the result. He thought this would
provide instantaneous and perfect control, as compared to error-driven
systems which could not even in principle achieve EXACTLY zero error.
That is, of course, not physically possible for any real system no matter
how it’s designed, including the systems Ashby imagined. But systems of
the kind Ashby finally chose are illusory, because simply expressing the
variable magnitudes as small whole numbers by no means shows that any
real system would behave in that sort of infinitely precise instantaneous
steps. 2 - 2 is zero in the world of integers, but in the real world it’s
anywhere between -0.4999… and +0.4999… . When you add 1 to 1 in the
real world, you get something close to 2, but not right away. Everything
in the real world takes time to happen, and Ashby chose an approach in
which that simple fact is ignored.
All this is a great pity since Ashby was one of my early objects of
admiration, and it took me quite a while to realize that his acquaintance
with real control systems was rather sparse. I think he just had the bad
luck to have an insight that led him straight off the productive path on
which he started. If he had been any kind of engineer he might have
realized his mistake, but he was a psychiatrist and more of a hobbyist
than an engineer. And like many in cybernetics in the early days, he was
engaged in that very popular contest of seeing who could come up with the
most general possible statements. What a coup, to boil it all down to
“Only variety can destroy variety”! Wow! And what a bummer to
be topped by Boltzman, who shortened that terse generalization by two
whole words. saying “Variety absorbs variety.”
Not my kind of game.