Like all of us, when facts are short, I rely on faith, intuition, prejudices and experience. We all do this, its how we think about things when we have insufficient data to form reasonable, testable hypotheses. It is also how we filter out the ridiculous and absurd from the merely improbable. It doesn’t always work, but as a wise man once said, the marker of true intelligence is the ability to make the correct conclusion when handicapped by a lack of valid information. At least, most of the time. Any asshole can arrive at the truth when provided with all the facts, but the ability to make reasonable judgements based on partial or incomplete information (at least, more often than not) is what distinguishes us from the beasts.
Here’s what I think about extraterrestrial intelligence. Again, my evidence may be circumstantial, but I believe my conclusions are reasonable given what we know, although I’ll be the first to admit I can’t “prove” them.
Organic life is common throughout the universe.
Advanced multicellular life, comparable to terrestrial invertebrates, is very rare.
Intelligent life no doubt exists in the universe, but I am convinced it is extremely rare, and compared to the average lifetime of the galaxy, is relatively short-lived. I believe at any one time in the history of our galaxy, there are at most a handful of extraterrestrial civilizations capable of space travel or some other technical means of making their presence known to their neighbors.
Due to the advanced age of our galaxy, any intelligent species is either way behind us on the evolutionary scale (they are simply critters, not a civilization; or they are so far advanced compared to us their technology would appear to us to be like magic, or a supernatural or paranormal manifestation, or some natural phenomenon, perhaps meteorological or biological.
When UFO enthusiasts describe ETI as arriving here in “ships”, they are displaying at best a lack of imagination. At worst, they’re blowing smoke out their ass. If such beings exist, they would either look and act like gods to us, or we would not even notice they were here. There’s a good possibility they might not even notice WE were here! The alien tech we hear about in UFO reports appears no more than a century or two ahead of our own, assuming our present accumulation rate of scientific and engineering knowledge. The idea they would be that close to us in technology in a galaxy 10 billion or more years old is absurd. The idea that they are humanoid in appearance is equally absurd. All we can say about real ETs is they are strange.
I have no idea what ET will be like, but I am training for their appearance using models from speculative fiction. Think of the protomolecule in “The Expanse”, or perhaps the shimmer in the film “Annihilation”. A few years ago I might have chosen “Space Odyssey” or “Solaris”. Even our wildest speculations tend to evolve over time.