[taylorius]

Why is it a fallacy to believe life is elsewhere in the universe? It seems the most likely possibility to me. Of course we have no proof either way - because we've not really looked anywhere (we're not able to, yet), apart from the moon, and a few tens of square metres of Mars (both of which we knew, a priori were barren rocks - but at least they're not too far away). That doesn't make the idea of other life in the universe "wishful thinking", surely?

[mr_mitm]

> It seems the most likely possibility to me

Why though? Surely you did not do a statistical analysis, because there are too many unknowns:

What is the likelihood of life (as we know it) forming on a given planet? What is the likelihood it will become multicellular? Life on earth was prokaryotic for billions of years and the Cambrian explosion is not yet entirely understood. How likely will it become intelligent? Remember, we don't have any reason to believe that intelligence is in any way a "goal" of evolution. Even if it does, will they have the resources necessary for becoming a technological species? Maybe dolphins are super intelligent, but living in the water and not having opposable thumbs sucks if you want to make tools and perhaps harness the power of fire to build even better tools and machines.

That does not even take into account the various catastrophic events that can happen in the universe where we do not have a good idea of how likely they are. What if a meteor hits at the wrong time? What about gamma ray bursts? What if a Carrington-type event wipes out all electronics? For all we know, these could happen with an average frequency of 100-200 years. Do we have an idea of how likely it is that the climate on a planet stays somewhat stable for a few hundred million years so it doesn't spontaneously become a planet like venus? We just don't have enough data points to assign probabilities there.

So yes, I believe it is largely wishful thinking.

[taylorius]

Ok, we don't know how likely life is to evolve in the universe. It could range from impossibly hard (though it cant actually be that, because we exist) to easy enough that it has occurred many times. Of all those possibilities, what difficulty range would result in it occurring once (on earth), but never again - despite the billions and billions of planets that exist. A very, very fine tuned difficulty - or to put it another way, the earth would need to be super,super unique, to be the only place capable of life in the entire universe. That strikes me as less likely that it occurring multiple times.