what is life?

Paul Schlosser SCHLOSSER at ciit.org
Wed Feb 23 11:29:10 EST 1994


In <2kfit3$a6e at mserv1.dl.ac.uk>
suter at VAX.MPIZ-KOELN.MPG.d400.de writes:

>+In article <2k8bt7$nqb at usenet.INS.CWRU.Edu> ef949 at cleveland.Freenet.Edu 
>+(Mark Petrie) writes:

[snip]

>+There are real, though remote, possibilities of finding life or
>+remnants of life elsewhere in this solar system within our lifetimes,
>
>i doubt this already ! there is no indication what so ever that nucleic
>acid based life, or any other form is present outside our planet. and
>the presence of 'simple' carbon based molecules is no proof either.

Do you doubt that the possibility is remote?  Or that there is a possibility?
Agreed that the probability is small, but 10^-10 is still not zero.
I'd say that we do not *know* and will not *know* until we explore the
possibility.

>naturally we should keep our eyes open for the unexpected. i will be the
>first one to admit that our definition is not broad enough, if e.g. 
>intelligent signals from outerspace would manifest itself completely 
>independent of nucleic acids (this excludes computers, hehehe). 

But how can we keep our eyes open if our definition closes them?

>but as long as
>no one can show me a putative lifeform that does not adhere to the nucleic
>acid definition, why should we broaden it ? 

Because we want a hypothesis for properly designed experiments in the
exploration of our universe.  If our hypothesis is "life does not exist
outside of the earth" (the null hypothesis), then, in order to disprove the
hypothesis, we must 1st define "life" in such a way that does not exclude
other possible alternatives.

>computer viruses, extra-
>terrestrials and chain letters, ok, it is funny to think about, and to look 
>at them as lifeform imitations, but perhaps you could come
>up with some arguments WHY they are alive (i didn't follow the discussion
                                     ^^^^^
>completely, i am sorry. perhaps a summary would be timely ?).

But we cannot even begin a discussion about whether or not they are "alive"
until we define what we mean by "alive".  And if the definition inculudes
nucleic acids then you are by default already excluding these things - the
argument becomes circular; e.g, you define "life" as incorporating nucleic
acids, so any alternate definition must be untrue because it doesn't include
them.

How about providing some arguments as to why computer viruses (those that
can change there own structure/program to adapt) are *not* alive?  If you
must use "they don't use nucleic acids" in your argument, then you have
fallen into this circular trap, your eyes are closed to what we might discover
in our solar system and beyond.

You say that if you are shown a real example of something that is "alive",
but does not use nucleic acids, then you would be willing to broaden the
definition.  Well, how will you *know*, when shown this thing, whether or not
it is truely "alive"?  What characteristics must it have, even if it doesn't
have nucleic acids?  What I am asking of you is to provide the criteria by 
which you will distinguish between that which is truely alive and that which
only has the "appearance of life."

Paul
schlosser at beta.ciit.org



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