[tgarv]

I've always wondered about this too, but kind of landed on something like this:

Sure, there might be (and probably is) life out there that falls so far outside our definition of "life" that we would never detect it. If it's undetectable, and maybe even incomprehensible, to us, then what's the point in even thinking about it in the context of a "search for life"? What we really mean by the question "Is there life out there?" is "Is there life out there that's similar enough to the life we see on Earth that we could recognize it as such and interact with it?"

I don't have a good way to phrase what I'm getting at without sounding dismissive - I do think it's interesting to think about other forms of "life", but it seems almost philosophical at that point and not scientific.

[tsimionescu]

Honestly I think similarity is a bit of a red herring. The most interesting question is whether there are other beings we can communicate with in any sense of the word, so that we may learn from each other. For a somewhat trivial example, if we found robots on another planet, we would not consider them "life", but it would nevertheless be an incredibly important discovery.

On the other hand, it's of course imaginable that there are beings that we would in principle consider intelligent agents, but who exist in a way that in practice we have no hope of recognizing as such. Again to pick a somewhat trivial example, if galaxies were in fact intelligent beings that take billions of years to form a single thought, we may both in principle be very interested in communicating with each other, but in practice could never even hope to recognize each other as sentient beings, because of the intense difference in time scale.

[CRConrad]

> Honestly I think similarity is a bit of a red herring. The most interesting question is whether there are other beings we can communicate with in any sense of the word

Much the same thing, as I read it: I think the GP meant "similar" in the sense of "alike us in that it even does 'communicate' in any sense in the first place".

[mekoka]

There are certain questions that are so stubbornly elusive to science (as the study of nature), that they should feel by now to belong to the realm of philosophy (e.g matter, consciousness, mathematics, an infinite universe). The study of life itself, not its manifestation in nature, has so far displayed all those fleeting qualities.

But I guess science is stubborn too, so let's see where we get.

[CamperBob2]

See the 'God of the Gaps' argument. At any given time, there has been a list of things considered to be the rightful domain of philosophers and theologians rather than logical positivists. So far, the list has only gotten smaller.

[nsv]

In other words - if you can't observe it, does it really exist?

[CRConrad]

"If a tree falls on your head in the forest, but I can't hear you scream, do I care" kind of thing? ;-)