Re: machines vs. living systems

[Tim Gwinn <***>]

Glen,

> > TG: Briefly, 'machine' refers to a sub-class of 'mechanisms' in the
> > Rosen terminology. Mechanisms are systems all of whose models are
> > simulable (i.e., Turing-computable). Machines are mechanisms which
> > additionally admit relational descriptions. The class of mechanisms
> > is in the class of 'simple systems', so machines are therefore also
> > simple systems.
>
> Excellent!  Thank you.  That took me directly to the relevant part of
> Life Itself.  However, I have some questions about this both practical
> and philsophical.


TG: Have you read Life Itself yet? That would help answer many of your
questions below.


> > To say that life is not a machine is to say that living organisms are
> >  physical systems whose models are not all Turing-computable; in
> > other words, they are not simple systems, but rather, Rosennean
> > complex systems.
>
> I can't see how this makes a practical difference when dealing with
> natural systems.Use a gas engine as an example.  There exist models of
> such an engine that are certainly simulable (effective).  But, there
> also exist models that are not.  For example, an engine consists (in
> full dynamic glory) of things like metal crystals, gasoline, fire,
> electricity, magnetism, oil, "sludge" that builds up on the spark plugs,
> rubber (or some rubber-like synthetic) in the belts, fluid vapor
> mixtures and dynamics, etc.
>
> A realistic enough model of this system will not be simulable.


TG: The set of models for a system are dependant upon how the system is
defined. Define it to include aspects like atomic interactions and you can
wind up with a complex system. Define it in coarser terms like pistons,
crankshafts, etc., then it is a simple system. You must be precise in your
system definition. It does not suffice to talk about 'practical'
differences - that is too vague.


> For Rosen's more formal use of the term "machine", it makes me think
> that "machines" are platonic and will only help in the world of
> formalisms and inference.


TG: 'Machines' are not discovered in the world, they are defined by us, and
we then realize them from these formal descriptions. We build computers to
conform to formal definitions, such as Turing-computability.


>  The term loses meaning when applied to the
> dirty world of reality.


TG: The formal system 'machine' and the material realization of it are not
the same system. You are trying to equate the two while simultaneously
applying a different system definition to the material system, so of course
they will then differ.


> > Because the term 'machine' is used in a very specific and narrow
> > sense here, this may clarify the distinction made here between
> > machines and living systems. If not, just ask some more questions. :)
>
> I wouldn't want to separate the specific sense Rosen uses from the
> vernacular sense... or at least I wouldn't want to overly separate them.


TG: You have to. When the line is not clearly drawn is when confusion sets
in.


> I'm not aware of two formulations.  I'm referring to "Theory of
> Self-Reproducing Automata".  What was the other?

TG: There is a kinematic automaton version and a cellular automaton version.

Regards,
Tim