Mark, it's not conceit. It's lack of evidence. Can you please direct me to concrete evidence that there are UFOs under the sea and earth's crust, or there are still "other civilizations on Earth" that produce UFOs? I respect your opinions but find such assertions incredible. I don't think they are based on facts. But may be I'm ignorant. That's totally conceivable. So, if I'm provided the factual evidence, I'm ready to change my views and learn from my error. Possibility (whatever the mind can imagine) is not probability. And what is probable is not necessarily a fact. Lastly: the burden of proof should be on those who make the claim that something exists, not on the listeners/readers of the claim. Otherwise anyone can claim anything at any time. Do we want to live in a world like that?