So you think it's possible for there to be an unknown species on earth, past or present
Not just possible, actual and factual!
that is capable of building flying saucers
As i said, that is not fundamentally impossible. Of course, there is no evidence to support it.
but aliens are not possible?
Correct. Because aliens only exist in modern fiction! It can't be elves from the lord of the rings either, for the exact same reasons.
Fictional things can't build or fly anything in reality. It is completely impossible, unlike the possibility that some cryptid (or even already known non-human lifeform) is responsible - which is merely preposterous/ridiculous (and evidenceless)
Not just possible, actual and factual!
As i said, that is not fundamentally impossible. Of course, there is no evidence to support it.
Correct. Because aliens only exist in modern fiction! It can't be elves from the lord of the rings either, for the exact same reasons.
Fictional things can't build or fly anything in reality. It is completely impossible, unlike the possibility that some cryptid (or even already known non-human lifeform) is responsible - which is merely preposterous/ridiculous (and evidenceless)