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and their configurations. On Ashby's definition, the variety of a machine was
defined precisely as the number of distinguishable states that it could take on.
This put Ashby in a position to make quantitative statements and even prove
theorems about the regulation of one machine or system by another, and pre-
eminent among these statements was Ashby's law, which says, very simply,
that “only variety can destroy variety” (Ashby 1956, 207).
To translate, as Ashby did in
An Introduction to Cybernetics
, a regulator is a
blocker—it stops some environmental disturbance from having its full impact
on some essential variable, say, as in the case of the homeostat. And then it
stands to reason that to be an effective blocker one must have at least as much
flexibility as that which is to be blocked. If the environment can take on twenty-
five states, the regulator had better be able to take on at least twenty-five as
well—otherwise, one of the environment's dodges and feints will get straight
past the regulator and upset the essential variable. I have stated this in words;
Ashby, of course, used his new machine notation as a means to a formal proof
and elaboration; but thus Ashby's law.
To be able to make quantitative calculations and produce formal proofs
was a major step forward from the qualitative arguments of
Design for a Brain
,
in making cybernetics more recognizably a science like the modern sciences,
and it is not surprising that much of the later work of Ashby and his students
and followers capitalized on this bridgehead in all sorts of ways. It put Ashby
in a position, for example, to dwell repeatedly on what he called Bremer-
mann's limit. This was a quantum-mechanical and relativistic estimate of the
upper limit on the rate of information processing by matter, which sufficed
to make some otherwise plausible accounts of information processing look
ridiculous—they could not be implemented in a finite time even if the entire
universe were harnessed just to that purpose.
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But there I am going to leave
this general topic; Ashby's law will return with Stafford Beer in chapter 6.
54
Cybernetics and epistemology
I have been exploring Ashby's cybernetics as ontology, because that is where
his real originality and certainly his importance for me lies. He showed how
a nonmodern ontology could be brought down to earth as engineering which
was also brain science, wth ramifications extending in endless directions.
That is what I wanted to focus on. But Ashby did epistemology, too. If the
Ur-referent of his cybernetics was preconscious, precognitive adaptation at
deep levels of the brain, he was also willing to climb the brain stem to discuss
cognition, articulated knowledge, science, and even painting and music, and
