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From: Bjoern Guenzel <b.guenzel@ucl.ac.uk>
Subject: Re: Proposed test for life
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Date: Fri, 4 Oct 1996 16:29:51 GMT
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Jim Barr wrote:
[...]
> 
> I totaly agree. Maybe that is it, maybe alife is life, but I am not
> happy about it

I guess the most complex A-Life Forms a still millions (thousands?) of
times less complex than the most simple life form? Perhaps that's a
reason for uneasiness? And they are not autonomous, that might be a
difference to real life. Sorry for my lack of knowledge, I am new to
this, I hope I don't annoy anybody with my unprofound comment.

> >  Sure
> >enough you can come up with a description, and even a physical theory that
> >predicts those motions.  But the theory won't pass the test of Occam's razor.
> >It turns out to require far too many a priori constants.  Newton's theory of
> >gravity started with a very simple model/definition that ended up predicting
> >the planetary motions with high accuracy, with essentially two constants: the
> >Sun's mass and the gravitational constant.
> 
> Ah yes Occam's razor, I believe in using it as well, The only problem is
> that it only works if all the explanations that you apply it to include
> the right one. What if our group of tests or definitions of life do not
> include one of the right ones. ( note I include a plural opportunity)

Occams razor would interest me, is there a way to explain briefly what
it's about?



> >        I personally lean towards a definition something like this:
> >
> >        "Life is the capability of a system for dynamic persistence."
> >
> I like that, it has the required simplicity

It's nice, but I have the feeling it is very vague? But perhaps this is
only because of my lack of knowledge of English. If so, sorry.

> 
> >        Dynamic persistence would mean the tendency to continue existence and
> >functionality in the presence of a changing environment.  A non-reproducing
> >organism that metabolizes (say, a castrated male frog) would be alive even
> >though it can't reproduce.  A frozen bacterial spore would be alive even
> >though it neither reproduces nor metabolizes, because it persists and is ready
> >to begin functioning again as soon as it thaws out and finds itself in the
> >presence of water and nutrients.  A brush fire or a prion would have a much
> >lesser capability for dynamic persistence, and would therefore be less alive.

I don't know, without food no life form would exist much longer than a
bush fire (Hm, on the other hand, I just remember those small eggs that
can survive thousands of year until they finally awake in salt water.
OK, that's more than a bush fire could do).


> >
> Yes, a fire given any amount of time to evolve would not select out/in
> mechanisms to accomodate drastic changes in fuel type,  or would it?

I guess fire already can feed on almost anything that organic life forms
can feed on, plus a few more things. How many life forms can feed on
anorganic food?

I am not sure if this selecting, evolving etc. criteria is really that
much important. I don't see myself as a replicator...(only joking). But
suppose it was possible to build a real artificial intelligence inside
of a Computer. Theoretically it could live (or wouldn't you say live?)
forever, what need to replicate should it have? My only idea (I just
make this up spontaneously): Drawing an analogy from the evolving and
competition of ideas and information to the struggle of Genetic
information... Perhaps the act Thinking can substitute for the
'evolving' criteria? 

>
[...]
> 
> Fraid your right, Steve, I am not one of them but I do see their point.
> There is something entirely reasonable about saying a virus is alive and
> a bush fire is not, but I cannot see why
> >

This is why I originally respond to this message (perhaps I should have
left out my other unworthy comments?)

I wonder if a virus is really alive? Is it not merely a piece of
information? Sorry, my knowledge of Biology is very small. But what
actions other than existing does a virus do? I only ask, because I guess
it would make things easier if for example virusses (viry??) could be
excluded. Or, if not exclude the virus, perhaps it all only melts down
to a question of 'information processing'? Perhaps that distinguishes
a-life from real life, for I think organic cells come with their own
Computer (whatever does the gentic processing thing)?

> 
> Thanks for the debate, where did all the others go?     Jim

I admit I felt invited by this line, although I didn't participate in
the original debate ;-)

> 
> Jim Barr         Machine Conversation, Bedfordshire England
> 
>                  Best is the enemy of good enough
> 
>                  Leaves Rustle....Blades turn..... Water moves


Bjoern Guenzel, only a poor student with no references ;-)

