Most definitions of life are very arbitrary. When it comes to astrobiology, we mostly look for things that look like us because if we didn't, the search space would be incomprehensibly large and frankly there's not a lot we could say.

My guess is that it had to do with avoiding a definition under which things like fire were alive.

I'd rather exclude fire on the basis that it's "reproduction" involves nothing like heritability.

Should it? Doesn't it inherit 'fireness'?

I do know what you're saying but it's so easy to argue the other way too

Yeah definitions are tricky. If you saw a house consumed with fire, you might look at the circumstances and conclude that it was likely the offspring of the fire that consumed the house across the street, but there wouldn't be anything about the fire's phenotype that would help you come to that conclusion.

If the flames carried the characteristic shape of their parents fire, and they could be distinguished as not the offspring of some other fire by their features alone, then I'd be arguing that fire is alive.

I feel like I'm at risk of classifying certain periodic crystals as alive here, but they wouldn't meet the thermodynamic requirements that I have in mind (which fire does meet).

Not to be a dick (oh, go on then!):

> but there wouldn't be anything about the fire's phenotype that would help you come to that conclusion

but... but... cloning!

But yes, we could do this all day and still get nowhere. We, collectively, are missing something but I don't know what.

Complexity theory comes to mind. Self-similar encapsulates that combine to create emergent behaviors.