Re: machines vs. living systems

[Tim Gwinn <***>]

Glen,

GR: What I don't understand is this distinction between "machine" and ... 
well, "non-machine".  What do you mean by "life is no machine"?

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.

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. 

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. :)


GR: To set a little more context for the above question, I'll add that I 
think of something like von Neumann's self-reproducing automaton as both 
a machine _and_ an artifact that attempts to tacitly demonstrate a 
common theme in Rosen's writings.

TG: As I understand it, there were two very different formulations of
"self-reproducing" entities discussed by von Neumann. Can you elaborate on
the one to which you are referring?


Regards,
Tim