> Why would finding life on just one more planet – out of the 195 or so "worlds" that we know about, including moons – suddenly make "the probability of life gi

> Why would finding life on just one more planet – out of the 195 or so "worlds" that we know about, including moons – suddenly make "the probability of life given a planet" high? Because sampling. It's like election polling. If you ask one person who they're going to vote for and they say "Candidate A", you really have no idea how likely it is that candidate A has massive support. Perhaps you just happened to find the only person voting for that candidate! But if you ask the next random person and they say the same thing, well, the odds that you found the only two people voting for candidate A in your first two random asks is very low. On the other hand, if the second person is not supporting candidate A, that also helps you get a better guess at support levels. You can never know the true level without asking every single person, but with every additional piece of data you can better estimate just what the truth is. Just the same, as soon as we find another star with life, the number of stars we had to search to find that second one gives us a fantastic start to coming up with an estimate on how common life is. We presume that our corner of the universe is a good sampling of the rest, and extrapolate based on what we know here. The key point is that extrapolation from a single data point is wildly innacurate.