what is life?

Paul Schlosser SCHLOSSER at ciit.org
Thu Feb 24 09:05:18 EST 1994


I'll reply to Clemens Suter-Crazzolara's message without re-listing it, as
it's getting to long.

The fact is that I really don't know what a good definition of life would
be, I was hoping to prompt someone else into coming up with one for me ;-)

I recognize that this is indeed a religious issue in that, in the Judeo-
Christian view, life is created by God and God alone, therefore anything
created by humans must be not alive, but a machine.  I disagree.

I would argue that viruses, both computer and biotic, are in fact alive,
though in a more limited way than plants and animals.  Both require a host
or very special environment in which to survive and replicate.  Removed
from that environment they cease to function and can be irrevocably destroyed.

Just because every thing that is "universaly" accepted as alive today uses
nucleic acids is not a good reason to restrict the definition to nucleic
acids.  There was a time (I believe) when all mathematics was Cartesian, but
it would be silly to confine our definition of mathematics to only those
systems/spaces that have been studied to date.

I'm repeatedly hearing people say "if you show me a form of life based on
something other than nucleic acids, then I will expand the definition."
Underlying that statement is the fact that the person making it has, perhaps
in a way that they cannot (or will not :-)) articulate, a definition of what
is alive, a "picture" of "life".  If that person is shown something that fits
this picture, but is not based on nucleic acids, then they will expand their
formal, stated definition.  My point is that it is this "picture" which is
in fact the definition that is being used, and it doesn't exclude things that
are not based nucleic acids.  In fact that picture hasing nothing to do with
molecular biology or chemistry.  That "picture" is the definition that most
of us are taught as a child: it ingests, it excretes, it procreates (makes
almost-copies of itself), it grows.  Now though, we are challanged by 
structures, computer viruses, which essentially fit the word-definition I just
gave, and even this internal "picture", but which fly in the face of the Judeo-
Christian belief that life can only be created by God.  So, if we want to
maintane that religious belief, then we can add to the definition "and has
arisen (or could have arisen in the case of transgenic beasts) without the
action of human beings.  Even there, we must add the "could have arisen"
because we are, right now, creating life forms that did not exist before and,
in all likelihood, would never have arisen without our action, although they
are a fusion of things that are now, without argument, accepted as alive.

Now, one more point before I offer my definition:  computer viruses have a
physical structure - electrons existing at specific locations in space.  They
are not "physical" in that we cannot pick them up in our hands (unless we
pick up the computer), but we do have instruments which can detect their
presence and determine their charaterstics.

So,
Life:  a physical structure that interacts with it's environment and is
capable of replicating itself so long as it's environment is not altered by
outside forces to a condition outside of an open set of conditions containing
the environment.

Thus, we can maintane a culture within certain conditions (e.g., temperature
range) but if we through our own stupidity, alter conditions on earth such
that all of the nucleic-acid based life becomes non-viable, then we don't
have to say that all this "life" was not alive just because it didn't replicate
itself into eternity.  "Life" on earth is maintained by a fairly constant
input of energy from the sun and by the fact that conditions here do not
vary too widely.  The fact that it can be "turned off" by changing those
conditions by a large extent doesn't make life any less alive.  Of course some
organisms can only live in a very small range of conditions.  So, the fact
that computer viruses require a continual input of energy from an outside
source, and can be eliminated by shutting off that source, should not also
exclude them from the definition of life.

Now, if we accept computer viruses as "alive" then we are faced by a moral
dilema.  But we should not exclude them just because we want to avoid such
a dilemma!  Now, just as I will swat any biting insect that lands on me, so
to I have no reservations about deleting any self-replicating physical
structure that enters my computer and discomfits me, so this potential dilemma
is not very serious in my view, but it may be to some.

Finally, as to chain-letters:  they are not *self*-replicating.  Viruses
self-replicate in a host, but do not require any special action from the
host to do so, the host must just continue to operate as it did before being
invaded by the virus.  Now if we come up with something that lands in our
mail-box, copies the return addresses of all the other correspondance there
and then makes copies of itself addressed to those return addresses (relying
on the post-office to deliver them) then *that* would be alive.

Paul
schlosser at beta.ciit.org
(you can tell that these are my opinions because they're so crazy.)



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