If you've actually read about it, it's pretty clear that Atlantis was wholly fictional to the ancients. It has only been believed in, as a real lost land, by the denizens of the industrial and post-industrial ages.
Like all myths, it has been believed only by those who found a use in it. So the cynical unbeliever must ask himself: what need of a fabled lost world would fulfill something in modern man but offer almost nothing to his pre-industrial counterpart?
I despise glorification of the past or present, but there is illness that may not have simply gone undescribed in past ages, but perhaps had not yet found our world so ripe for infection. And one must only look to the diseases of our body to realize something even more frightening--
The mind has always been more fertile a home to disease, more so even than our feeble bodies.