Any estimations about life outside Earth only become viable once we understand the factors that gave rise to it first, and their probabilities of occurrence. If

Any estimations about life outside Earth only become viable once we understand the factors that gave rise to it first, and their probabilities of occurrence. If the total probability is less than 10^24 (say) we might expect life elsewhere, but if it's 10^100 probably not. But either way, gut feel and intuition about this are pointless - by the anthropic principle, we're speculating about the possibilities of life only because we're already winners of the lottery - almost like someone lucky enough to win a lottery twice or thrice in a row wondering why it doesn't happen to everybody. Either way, I actually think that the Dark Forest principle applies heavily in the universe (https://en.wikipedia.org/wiki/The_Dark_Forest https://en.wikipedia.org/wiki/The_Dark_Forest) - no halfway intelligent civilization should assume the intentions of any other civilization are benign until proven to be so, and will always take steps to either hide themselves or shoot first and investigate later.