The great filter is whatever obstacles prevent simple dead matter from evolving into a civilization big and visible on astronomical scales. The fact that we see nothing big and visible in a huge universe says this filter must be large, and a key question is the size of the future filter: how much have we passed and how much remains ahead of us?

I’ve suggested that evidence of life elsewhere below our level makes the past filter look smaller, and thus our future filter larger. From which you might conclude that evidence of a civilization above our level is good news. That seems to be what Dylan Matthews says here at Vox:

If (and I must stress that this is a quite unlikely “if”) UFO sightings on earth are actually evidence that an advanced alien civilization has developed a system of long-distance probes that it is using to monitor or contact humanity, then that would be an immensely hopeful sign in Great Filter terms. It would mean that at least one civilization has far surpassed humanity without encountering any insurmountable hurdles preventing its survival. (more)

But I don’t think that’s right. This would move the filter more to above their level, but below the level of becoming big and visible, without changing the size of the total filter. Which implies a larger future filter for us. In addition, any UFO aliens are likely here to actively impose a filter on us, i.e., to stop us from getting big and visible (or “grabby“).

So if UFOs as aliens is not good news, what would be good news re our future filter? Aside from detailed engineering and social calculations showing that we are in fact very close to becoming irreversibly grabby, the only good news I can imagine is actual concrete evidence of big visible aliens civilizations out there. Maybe we’ve misread their signatures somehow.

Looking out further and in more detail at the universe and still finding it dead suggests the total filter is larger, which is bad news. And finding any evidence of anything other than death suggests the filter is smaller up to the level of that finding, but doesn’t revise our estimate of the total filter. Which is bad news re our future. Thus a perhaps surprising conclusion: finding anything other than a big visible civilization out there is bad news re our future prospects for becoming big and visible.

Remember also: the SIA indexical prior (IMHO the reasonable choice) favors larger future filters. Beware the future filter!