especially as we could simply have missed fossils/their not have been formed for the post-fish stages
and focus on the purely theoretical argument. Assume our degree of belief that the Great Filter is ahead of us is X. Now we land on a new planet. If we find no evidence of life at all, X is unchanged. If we find some fossils at whatever stage, or any life at all (except an intergalactic civilization which we would’ve noticed before), then according to your reasoning, X should increase. This violates the Bayesian law of conservation of evidence, as X can only increase and never decrease.
Let’s disregard this:
and focus on the purely theoretical argument. Assume our degree of belief that the Great Filter is ahead of us is X. Now we land on a new planet. If we find no evidence of life at all, X is unchanged. If we find some fossils at whatever stage, or any life at all (except an intergalactic civilization which we would’ve noticed before), then according to your reasoning, X should increase. This violates the Bayesian law of conservation of evidence, as X can only increase and never decrease.