Steve...

"There has never been any form of communication with aliens, in spite of alleged frequent visits to our planet by UFOs."

Oh, really? ;-) I think there has. It just isn't on your 6 O'Clock News report every day and it's not on the front headline on your newspaper. In other words, it hasn't been made "official" yet by the powers that be. They do not wish to publicize it.

"There is no evidence of any effect "they" have ever had on us."

Says who? That all depends on who you talk to. I gather that you have not seen any such evidence yet? ;-) I doubt that you ever went looking for it either. Where would you be likely to find something if you never bothered to look for it?

"There has never been a single really convincing photo or video of a UFO or an alien."

There most certainly has. Many of them. However, again they are not being officially acknowledged by the powers that be...meaning your mainstream media and your government. Oh, they might pay attention to an incident for a day on the news...but then it's on to the latest bla-bla about American Idol or North Korea or something.

Really, Steve, the willfully blind, deaf, and dumb do not make very effective sources of information. ;-)

"I pointed out the implausibility, according to the laws of physics, of their visiting us."

I don't know if it's implausible or not. That depends on whether we already understand everything there is to understand about physics or anything else. Indians once found it implausible to believe that tall wooden ships with towering masts and sails could come mysteriously out of the endless waters to the East and land on their shores, and men everywhere once found it implausible to believe that a manned and powered machine could fly. The "expert opinions" of those cultures turned out to be dead wrong in time about thoee things, didn't they?

"On the other hand, your "spaceships" were perfectly feasible human constructions."

Agreed. And they may have been just that.

"We have built airborne craft of all shapes, sizes, colours and materials."

Yes....

"Nothing you saw was humanly impossible, or even technically difficult to achieve."

Actually, you're mistaken about that. I saw those craft do things which are presently considered impossible, going by our current knowledge. This, more than anything else, caused me to think they were indeed alien, although it might just be that our scientists have come up with some really amazing stuff that they haven't uttered a peep about to the general public. If so, they are betraying a public trust. Either way...it's a coverup. They're either covering up alien visitations...or they're covering up extraordinary advances in Earth technology that would revolutionize our entire civilization.

"Your only evidence is that they were unexpected and unfamiliar."

Yes. And since then I have acquired a great deal more information from other people who have had similar experiences, and people I feel I have no reason to distrust. Professional pilots are among the witnesses I mention.

"We have to proceed through this complicated life somehow, and one good ploy is to go, with all appropriate doubts of course, with what are the most likely explanations, for now, for things, given the evidence we currently have."

Exactly. That's what I do.

"It's only you rattling on about "the truth," not me."

I am saying what I think is most probable, given what I have witnessed and other information I have consulted since then. So are you, only you seemingly haven't witnessed anything pertaining to the subject under discussion. Therefore, I can't see that you have much to go on, other than conventional thinking. It was conventional thinking that said man would never fly in a powered machine. Conventional thinking is what has stood in the way of every great breakthrough in human understanding ever since man first built a fire and learned to make a spear.