Ask a friend what they think of flat earth theory and the chances are you will receive some pretty derisory feedback. It's not a view of reality that gets people queuing up for tickets these days. Its two dimensionality has long been superseded by three dimensional models. People have seen pictures of the Earth from the astronaut and cosmonaut perspective: a rotating sphere rendered in the two dimensions of the photograph. They have seen globes in classrooms and living rooms. Flat earth theory is seen as a kind of rural backwoods of the mind, a dogged luddite strain that must surely proliferate only in the kind of primitive conditions where marriage is kept within the family and as a result children are born with Hapsburg noses and nine fingers.
A tenacious empiricism, on the other hand, is not seen as so primitive. Much thinking remains in the doubting Thomas mode: if I can't see it, smell it, hear it, touch it or taste it, then it doesn't exist. And even if I can see it, smell it, hear it, touch it or taste it, then I'm still not even sure it exists. Best to hedge your bets so far that all you really believe in the existence of is you, your television and your job, although you spend most of your time worrying that the last one will disappear leading to the disappearance of the middle one, and then possibly leading to the disappearance of the first.
Our human senses, and the dimensions that they operate within, are as limited as the theory which considers the earth as a piece of A4 paper suspended in a paddling pool. Take the electromagnetic spectrum for a moment. You cannot see gamma rays because they are moving at frequencies higher than our eyes are manufactured to pick up (that phraseology is not quite accurate, but it serves to illustrate the point). Our everyday empiricism clings to the narrow bands within which our basic senses operate and calls this reality. Even when we create new technologies which are extensions of our sense organs and nervous systems, thus extending the bands within which we can perceive, even then we assume that the limits of these bands are the edge of the flat earth - the edge beyond which there may be dragons, or perhaps an abyss, beyond which our ships will fall off and we will all die.
In Marshall McLuhan's term, people are viewing reality (or, better, a multiple web of interlinked realities) through a rear-view mirror. Or a number of rear-view mirrors. If there are dimensions beyond the range of the general human visual spectrum, could our everyday empiricism not be a form of flat earth theory? Edwin Abbott, a Shakespearean scholar in the 19th century, wrote of a country where everything and everyone is perfectly flat. He called it Flatland. There is width and length, but no height whatsoever. If a three-dimensional creature entered Flatland it could only exist partially there - in a sense, it would exist as a cross-section because only a cross-section of its three dimensionality could be perceived. But does that mean that its third dimension doesn't exist? Well, in a sense it does because most of the Flatlanders do not perceive its existence, and seeing is believing. But perhaps there are some Flatlanders who learn to trust their instinct that there is an 'above and below' after all.
This is where, I think, ghost stories become so attractive. Because they hint at dimensions not perceived through what we see as everyday perception. In fact there are many paths to a deeper perception. Some are seen as lunacies, some are illegal, some come through drugs, some are recognized with diplomas, some happen at séances, some involve particle physics, some involve poetry, some involve sex. In fact there are as many paths up the mountain as there are snowflakes on Mount Everest right now. But there is really only mountain, from all which all other revelations derive: the mountain peak realization that life and death are illusions from a perspective beyond what we think of as everyday human senses. That you, and your friend who mock turtles flat-earthers, and me - we're all exisiting in several dimensions. And what we call Earth or everyday life is really only a segment, like the little band of rainbow colors we call the spectrum of visible light.