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I suspect the entire argument is bogus, but I haven't been able to prove it yet.

The argument you're making is called a "Strong Anthropic Argument", which tries to infer some property of the likelihood of your existence from the fact of your existence.

There is a related line of argument: "Weak Anthropic Principles" (in this case weak as in it doesn't try to claim as much.) Weak Anthropic principles must be true. (Arguments of the flavor of "I think therefor I am".)

Wherever you go, there you are. Whatever sort of world you find yourself in must be a world that you *can* find yourself in.

Strong Anthropic Arguments have a problem with them though, and the problem is this: You can't define any measure over the set of possible situations that you find yourself in. Bayesian Reasoning isn't going to help you, because you can't define a prior probability. (No reasonable symmetry to use to distribute prior probability over a set evenly. Unless you've reincarnated a few times, you have no Frequentist sampling with which to develop a prior probability.)

(At least, I think that's what these two were called. I may be wrong. Engineer, not philosophy major.)


"Rather than disproving the existence of ancient starfarers, maybe life on Earth is evidence they stopped off here."

There's an infinite regress problem with this one. If the existence of life is evidence that it must have originated elsewhere, then there isn't anywhere where it could have originated. (Elsewhere keeps moving.)


PS: Not trying to nitpick or find fault, just trying to engage with your article.


Oh, absolutely: panspermia doesn't explain the origins of life. But it does change a lot of the assumptions. If ancient aliens seeded the whole Galaxy, that means either intelligence is even less common than I posited . . . or there's some kind of really potent Great Filter about to filter us out of existence.


As per my input on Centauri dreams one needn’t harness the power of a star to send a clear message. Here on earth in 2020 sober and rational types are discussing solar shades in orbit around the earth to address global warming. In a couple of hundred years it should be a realistic discussion to orbit larger shades around say alpha Centauri to form an unambiguous and clearly artificial optical message along the galactic plane. Keeping shades on orbit takes energy, yes, but not at the level of requiring the full output of a star. It seems to me that signaling can be done both relatively inexpensively and with tech not too far removed than our present capability. As such the lack of seeing a clear signal suggests we’re alone.

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