Newsgroups: comp.ai.alife
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From: stevens@prodigal.psych.rochester.edu (Greg Stevens)
Subject: Re: "What is Life?"
Message-ID: <1995Feb8.053325.28638@galileo.cc.rochester.edu>
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Date: Wed, 8 Feb 95 05:33:25 GMT
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Brian Holtz has described a view of life as being defined by the process
or ability of organisms to reproduce and evolve, noting that members of
a population that normally reproduces and evolves even though those 
individual members do not are still alive by this definition.

I have described a view of life as being defined by a system being made up
of a system of production componants that function self-referentially
(i.e. so that each componant in the system functionally is defined in terms
of it production of other elements within the system and the maintanence
of the structural relations within the ssytem) and have boundry-componants
that specify functional and spatial boundries.

Both of our definitions include normal biological life on this planet as
we understand it and exclude fire, tornados, crystals, etc.

Our definitions disagree on such things as the Tierra program, which
ONLY evolves and reproduces but does not have any of the internal
structural elements to each of the "organisms" characteristic of the
definition of life I've described.

I maintain that defining a term which properly applies to individuals
("X is alive" is a statement where X refers to an individual, not a 
population) in terms of population dynamics (evolution) is an error of
type and a confusion of catagory.  I maintain that life, being a
characteristic of individuals, should be defined in terms of the function
of those individuals and the structure they possess which gives rise to
that function.
  
Thus, to me an individual structure's self-production and self-maintanence
seems much more a contributer to my assessment of whether it is "alive"
than data about an entire population over extended periods of time would be.

Greg Stevens

stevens@prodigal.psych.rochester.edu

