Jim, thank you, and thank you again, I should have fixed the typo myself really, and I think this is a much more appropriate home for this thread.

Lepton: Swift has just put it much more clearly and succinctly than I had been managing. Now I've had some time to collect my ideas I realise I should at least amend the title to something more like 'Life has no single, specific origin'.

I would add to what swift has said that when we look at a system we do not insist that it's temperature be measured as either hot or cold, we give it a temperature in degrees something. I have begun thinking that, particularly for places like titan where many of the 'ingredients' for life are present and have been interacting in a complex way for a long time, a 'life temperature reading' may be more appropriate than a simple judgement of alive or not.
Complexity was simply my first thought for a criteria to use. That would mean even very simple systems might have to be assigned some degree of aliveness to make the scale consistent, which would fly in the face of accepted views on life as neverfly pointed out. As swift pointed out complexity may well not be the best criteria to use.

A further thought I was trying, and not really succeeding, to express was that some systems might show the 'higher' attributes of life, but not the lower. For example an AI could show intelligence, empathy, emotion and even intuition, but not be capable of reproduction or Darwinian evolution. This would present a similar problem to classifying viruses, in that although something is definitely going on in there, it doesn't fit neatly into the definition of life, and so a 'life temperature', or 'degree of life' would be a more useful measure to apply to it.

If we discover forms of 'weird life', using methane instead of water, or in the solid or gas state, they would also push the boundaries of what is considered alive. Instead of giving them long names like 'Darwinian information carrying, environmentally responsive dusty plasma phenomena' we could simply say its a plasma entity with a life rating of 6.5 ( or 6.5 for life criteria x, 5.2 for life criteria 2 .. and so on). I'm sure there are some fairly obvious core criteria, and a lot of less important but still useful ones to be added. Agreeing a list that could be accepted by most scientists would be a first step towards such as system, which could well be needed as we begin to explore stranger environments.

EDIT: Er... How do you change the threads title, I can't work out how to edit it, does it need to be done by a moderator?

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