[ExI] Silence in the sky-but why?

[Eugen Leitl]

On Tue, Aug 27, 2013 at 11:11:48PM +0200, Anders Sandberg wrote:

> OK, please hide under the cover: Stuart's and my paper multiplies
> the number of relevant stars by a factor of 10^6-10^9. So instead of
> one chance in a trillion of intelligent life, the above argument
> requires it to be one in a quintillion or one in a sextillion.

Rarity is not relevant for self-observation. Common as dirt
or infinitely rare, you can't tell in absence of an external
observer.
 
> Now, I am all happy with saying intelligent life might be rare. But
> given the growth of cephalization on Earth and the fact that there

Sample of one, perfectly biased.

> are several species that show a not insignificant problem-solving
> capability that could perhaps evolve into true intelligence in a few

You can't put a probability on any of the steps, until you have
a second, unbiased sample. So far, we don't.

> ten million years, it seems hard to argue that the step from life to
> intelligence is *that* low probability. So if you believe in an

And the answer is: we just have no idea.

> early great filter, it better be that life is amazingly unlikely.
> That might work.

All these probabilities are firmly pulled from /dev/ass. 
Exploration of this stellar system might give us a real probability,
but I think it's unlikely due to panspermia.