A possible definition of life.

Rob Miller rmiller at house.med.und.ac.za
Wed Apr 23 05:05:31 EST 1997


Ed Rybicki:
>    >     "Life (anywhere) is the phenomenon associated with th replication of
>    >    self-coding informational systems".
>    >

James Foster:
> I'm beginning to be a devil's advocate here, using absurd arguments
> only for illustrative purposes, but...

ok, staying in the same vein.

> 
> Suppose you put the wiring diagram into the copier.  Now the diagram
> and the copier together are a "self-coding informational system" and
> the phenomenon associated with what the machine is doing is life.
> 

Perhaps it's not fully specified in Ed's definition, but it seems to 
me that a `replicating, self-coding system' must include the complete 
replication details, including everything to actually do the replication
--
which the copier with wiring diagram doesn't.  We may also need a clause
that it be self-replicating in a specified universe, e.g. no additional
self-coding system (a human) required to come press the copy button 
(although we may allow that 2 or more of the original self-coding system
are required for complete replication capabilities).  Now, we could 
specify a copier with the copy button held down continuously, but it's
still not able to replicate *itself*, only it's coding.

> I meant phenomena (plural) because there are several things happening
> during replication, and Ed's definition fails to distinguish any of
> them.

sure, but don't the semantics allow us to group all these things into a 
single phenomenon, i.e. the very existence and functioning of such a
system ?

> 
>    > I remember a philosophy paper in college arguing that thermostats were
>    > alive: they are self regulating, have internal representations, must
>    > be in a host, etc.
> 
>    But they are not self-coding.
> 
> But they make the thermal properties of the house "self-coding".

but but but :-)  the original claim was that the thermostat was alive,
and 
this change still doesn't allow for any replication (of either the
themostat
or the house's thermal properties).


> And I've annoyed the alife "experts" before.  I think that most of

Horrors !  How can you sleep at night ?  :-)

> 
> ...I remain unconvinced that you need to define life in order to
> understand it. 

Ah, but what then will we understand (as `life' remains undefined)  ?


> The same is true in other disciplines.  You don't need
> to define matter in order to do physics.  You don't need to define
> energy in order to do chemistry.  The mode of operation where you
> begin with definitions seems to work best (and perhaps only) in
> disciplines like CS and mathematics (and philosophy)...where we're
> investigating consequences of definitions.

ooops, wrong ng -- I thought this was bionet.molbio.life.philosphy :-)


						rob.



-- 
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Robert T. Miller, Ph.D.                               
rmiller at sanbi.ac.za
Manager, Durban Satellite, South African National Bioinformatics
Institute 
Department of Molecular Virology,  University of Natal,  Durban, S.
Africa
h: www.sanbi.ac.za   p: +27 (0)31 2604580  f: +27 (0)31 3603744 or
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