One question Ethan… If not life, what?

As you’ve said, multitudes of planets, many comparable to Earth in all sorts of ways, ingredients of life everywhere…

How, then, do those ingredients behave, on worlds with similar start conditions to Earth’s, if they do not form a biosphere comparable to Earth’s biosphere?

You say that non-existence of other life is “the most conservative possibility of all”. I would have thought the most conservative possibility is that comparable start conditions on comparable planets bring comparable outcomes…