When we try to estimate the number of technological civilizations that evolved on main-sequence stars in our past light cone, we must not use the presence of at least one tech civ (namely, us) as evidence of the presence of another one (namely, ET) because if that first tech civ had not evolved, we would have no way to observe that outcome (because we would not exist).
If there were two universes, one very likely to evolve life and one very unlikely, and all we knew was that we existed in one, then we are much more likely to exist in the first universe. Hence our own existence is evidence about the likelihood of life evolving, and there still is a Fermi paradox.
If there were two universes, one very likely to evolve life and one very unlikely, and all we knew was that we existed in one, then we are much more likely to exist in the first universe.
Agree.
Hence our own existence is evidence about the likelihood of life evolving [in the situation in which we find ourselves].
Disagree because your hypothetical situation requires a different analysis than the situation we find ourselves in.
In your hypothetical, we have somehow managed to acquire evidence for the existence of a second universe and to acquire evidenc...
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