Not the same thing. This "silurian hypothesis" is not so much asking the question about the existence of a pre-human industrial civilization but rather to what

Not the same thing. This "silurian hypothesis" is not so much asking the question about the existence of a pre-human industrial civilization but rather to what degree we could rule it out. It's a rather implausible proposition, after all, so it would take extraordinary evidence. And that evidence might not survive that long? But this doesn't make the proposition more likely.