Fact is, there is currently no reliable or substantial evidence for the existence of life elsewhere.
True that, I think the probability that it's out there is enormous, but because of distance and time constraints, the probability that we would be able to get reliable or substantial evidence is almost zero.
Assuming that there should be is a reasonable assumption.
Science's primary method of reasoning is inductive reasoning, which moves from specific observations to general principles, and it yields probabilistic conclusions. Estimates of the number of planets with conditions similar to earth, are mind bogglingly large, billions in the milky way alone, and in the quintillions in all the galaxies in the visible universe. Let's go with statistical probability, we have only been able to observe one, and what we observe on that one is a natural process that included the creation of life which steadily progressed towards greater complexity and higher forms of sentience, going from inanimate matter, to life, to thought, to self-reflective consciousness, culminating in intelligent life. Out of a possible quintillion, we have observed intelligent life on 100% of those sampled, scientifically speaking, the probability that there are others is mind bogglingly high.
And suggesting that there might not be, is a reasonable suggestion.
I suppose it's reasonable, but I've never seen an argument that logically arrived at that conclusion scientifically.
Just like bigfoot, we see the indefinite photos, but it never strolls down the high street.
So if ET's are clever enough and have the technological ability to get here, then why keep fu*king about with all the sketchy unidentifiable introductions.
Yep, Fermi's Paradox, I think it's easy to come up with reasons why we wouldn't be able to detect life on other planets even if there are trillions and trillions of planets with life. I have a strong background in signal transmission and there's no fucking way you can get any known signal from there to here. I would think that it's even more impossible to get a vehicle from there to here, and yet, I saw one almost 60 years ago, and despite how unlikely or unreasonable the conclusion is, I have always believed it was evidence of extraterrestrial intelligent life. The whole point of a UFO is it's "unidentified", it's much more reasonable to conclude what we are seeing is some kind of terrestrial phenomenon that is merely unidentified and misunderstood.
Nevertheless, I'm going with little green men.