wrote:

> > From: john_SPAM{at}wilkins.id.au (John Wilkins)
> > the love affair we have with things digital is not, in itself, enough
> > to justify a separate metaphysical category or ontology.
> 
> The way a device works has nothing to do with metaphysics. Our language
> to lump that workingness into a category as a first approximation to a
> complete description, has nothing to do with metaphysics. Information
> storage or communication devices often work in one of two ways:
> - Linear amplifier over some range (analog)
> - Saturated amplifier with two or more attractors/basins (digital)
> It's quite clear to anyone who knows anything about genetics that DNA
> is anti-replicated on the basis of:
>   A -> T
>   T -> A
>   C -> G
>   G -> C
> and intermediate values between those four discrete values are "fixed"
> by either deleting that datum or coercing it to one of the four
> discrete values listed in the right column above. That is clearly a
> digital method, not an analog method. Mistakes are sometimes made, such
> as slipping the reading frame, so a base gets duplicated or deleted,
> but again the result is a sequence of digital data, not some
> intermediate analog value.

Mistakes also get made that show that this process is not digital at
all, but merely a high-fidelity analogue process - despite the bonding
sites, G can mispair with A and C with T. Also, other molecules can bind
and interfere with the physical processes of expression and duplication.
If we could see the process occurring we'd be a lot less disposed to
calling it "digital". The metaphor of the code has overtaken our ability
to conceive of this, in general.

Moreover, if we were watching the process of a "digital" signal being
laid down in a magnetic medium, fo rexample, we'd see an analog process,
with fuzzy edges and varying strengths. The "digital nature" of
electronic signals and DNA lies in the fact that both are checked for
"errors" by exogenous machinery (and corrections cannot always be made,
of course) and in the ways we describe them (with symbols, such as GATC
and 1 and 0).
> 
> Several other processes within a living cell related to the genome
> likewise operate per a digital model. In a case I saw on the net a few
> weeks ago, slipping the reading frame when anti-mapping DNS to mRNA
> occurs appx. 50% of the time when a sequence of nine consecutive
> all-same bases occurs, resulting in two version of a protein complex,
> which together make the entire protein. That is still a digital
> algorithm except for the analog-random-noise amount of slip before
> resynchronization converts the signal back to digital.

It is digital except when it isn't? I think you gave the game away.
> 
> Other processes are statistical in nature, with no locking into
> attractors, so even though the individual events are in some sense
> digital (an individual instance (molecule) of a catalyst makes a
> reaction happen some specific number of times before that catalyst is
> destroyed), the best model for the overall process is analog, some
> quantity of catalyst exists which causes some quantity of reaction to
> happen, with output something like a linear function over any short
> range of input, with gentle saturation near the ends of the function
> but no locking into those saturation points rather usually avoidance of
> saturation.

Atractor points need not be digital. Whatever gave you the idea that
they have to be? Sure, they can be *described* or *derived* using a
digital simulator, but we all know that the slightest differences in
precision can generate quite different outcomes in chaotic math, so a
physical attractor is not digital as such, just representable by a
sutiably high precision model.
> 
> By the way, the bag-of-lipids with set of replicators that we were
> discussing a few weeks as possible pre-life, worked in a
> statistical/analog way regarding frequencies (abundances) of the
> various replicators, but in a digital way regarding presence or absence
> of a particular replicator in a particular bag.
> (DNS should read DNA above, sigh.)

"Presence" and "absence" defined according to which
threshold? :-)
-- 
Dr John Wilkins
john_SPAM{at}wilkins.id.au   http://wilkins.id.au
"Men mark it when they hit, but do not mark it when they miss" 
                                               - Francis Bacon
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