Swetasuria said:
I have learned in my second grade that all things are categorised into living and non-living things. Living things breathe , grow, reproduce, etc., I don't really remember... and non-living things don't.
Our textbook used "stimulus response plus metabolism plus offspring" and then added "genetic material" because something like fire can match the first three, if one interprets the terms widely enough. The approach
Rooted mentioned is certainly more elegant, but I'm not convinced it actually solves the problem, since there's no obvious reason for all physical processes to be governed solely by current external conditions rather than past and present internal traits, which is presumably what "vary" means.
Swetasuria said:
I was thinking if there was something that isn't living or non-living; something entirely diiferent. I know about viruses: the threshold between living and non-living. Just asking, but what about stars? It is sort of like a living system, isn't it? It can't be 'completely non-living'.
I have actually read a publication making the case for stars being alive. Unfortunately, it was too long ago for me to remember enough about to be able to track it down, it seems. What I do remember is that it was a more or less scientific argument, without any recourse to mysticism, and that I ultimately didn't find it convincing.
That being said, it's not unusual for insect colonies to be considered life-forms. They certainly match the four criteria from my textbook, and they even in some ways display a higher form of intelligence than any individual insect, possibly not all that dissimilar from a multi-cellular organism displaying a higher form of intelligence than that of any individual cell. Furthermore, there doesn't seem to be any good reason to count only the insects themselves and not the nest they build and inhabit as part of that colony life-form, that I can see, just as one counts a snail's shell as part of the animal and not as clothing or housing.
If one accepts all that, it doesn't take much mental stretching to make a similar case for human communities and their homes, which when taken to its logical conclusion means humanity as a whole and the Earth, it would seem. In this view, the objection "it's not the Earth which is alive, it's individual creatures" doesn't make any more sense than "it's not humans which are alive, it's individual cells". And if one accepts the Earth as alive, then why not anything which contains it, i.e. the solar system, galaxy, and universe?
There's a non-mainstream cosmological hypothesis by
Lee Smolin which posits that every black hole gives rise to another universe. Based on that idea, universes can be thought of as producing offspring via black holes. Coincidentally, or maybe not, the same conditions that favour the production of black holes also appear to favour the emergence of intelligent life. From there, it again doesn't take a giant leap to consider a universe in its entirety to be alive. I seem to recall Smolin discussing that himself - and if I didn't, the name of his pop-sci book, "The Life of the Cosmos", would be a bit of a giveaway.
I'm not really saying that I subscribe to any of these views myself, but it seems clear to me that definitions of (life which don't take the drastic step of limiting life to the biological, terrestrial kind by adding some ultimately arbitrary criterion like "genetic material") tend to be a lot more inclusive than we ordinarily consider them to be.
