SM62,
You asked,
How do you know this? How do you account for all the weird sightings around the world? Are you saying the millions of people over the centuries who have had paranormal experiences such as seeing dead people are lying? Or are they all mad? I don't really know what to believe, but I always keep an open mind.
It is funny, knowing what we know of psychology, that people are so willing to believe that they are unimpeachable witnesses of supernatural events in the world outside their heads, rather than accept that emotional states, hallucinations, hypoxia, etc., could easily explain their experiences.
Do you believe in "cause and effect," or do you believe that we live in a world where "stuff happens" that is completely contrary to the rules of the real world that we depend on each day: when preparing breakfast, for example.
It may be tempting to believe that a world exists with no apparent rules, no apparent principle of cause and effect. Really, if you accept this baloney, how do you get through the day intact? How do you know that any particular experience is in the REAL world, and not simply the result of a supernatural deception? How do you know that the next time you pick up a pencil, it won't turn into a snake? ..or that you won't suddenly become quite tiny and fall into the ocean of coffee in your coffee cup? Or that your kitchen window won't start a conversation with you while your refrigerator dances the jig? These things might not be unexpected or impossible if there was a supernatural world. Do your dead relatives care so little for you that they won't tell you what the next XEROX-like stock will be, but they keep reminding you of the puppy who ran across a meadow?
I'm glad to hear that you have an open mind and are willing to consider that THIS world is IT.
I know that there is no spirit realm populated with any sort of intelligent, invisible, immaterial beings simply because there is no evidence of such a realm.
The principle of analytical thought known as "Occam's Razor" suggests that when there are multiple "explanations" for an event, it is likely that the simplest explanation is most accurate. In other words, why create an entire imaginary world to explain that you had a dream?
(for more about Occam's Razor, see http://pespmc1.vub.ac.be/OCCAMRAZ.html)
All (ALL!) of the progress of the human race has been the result of man's mind (analytical thought) and man's back (labor).
No supernatural manna has ever come from the great beyond, no miraculous city has descended from heaven.