The cited paper describes the hypothesis of “The Great Filter,” a
proposed explanation to Fermi’s Paradox, and the explanation I find the
most compelling. According to a hypothesis there is a Filter causing
potential civilizations to never attain interstellar colonization, but
where exactly this Filter lies is unknown.
If the Filter lies past us, if say, the Filter is the chance for life to originate then we’ve long
since past the Filter and have nothing to worry about, but if life is
common in the universe (this is the reason why some scientists dread
discovering alien life on Mars and Europa) then we haven’t reached the
Filter yet, and therefore have reason to fear.
In line with this hypothesis any positive result we get from SETI would be bad news, for
it means that since life is common, especially intelligent life, that
the Filter therefore lies ahead of us, and any negative results we get
from SETI are good news, for the Filter is long behind us.
Given the likelihood that we are not alone in the universe, what this means is that we have reason to fear for our future, and given that we are currently bombarding ourselves with a number of different threats (nuclear Armageddon and global warming being the two foremost threats we are currently subjecting ourselves to), the Great Filter may not lay that far off in our future.