One of the most important questions to resolve for anyone living on this planet is, in my view, the existence or not of a spiritual realm or dimension, in addition to the physical. Connected that to question is, of course, whether or not we ourselves have eternal spiritual selves, in addition to the physical.
The reason I include the word "eternal" is because some people may conceive of the spirit as a type of life force, but which would dissipate with the expiration of our physical lives. In that view the spirit would be a type of energy, seemingly nebulous, but still as much a part of the physical universe as the trillions of elusive and minuscle particles whizzing around and even passing through us every which way.
Many scientists working in the area of physics have long sought a "theory of everything", that is, a simple and elegant formula that could provide an ultimate explanation for our universe. Some think that finally trapping in a jar the long-pursued Higgs Boson would be a key step in validating existing theories. However, these theories completely ignore the possible existence of a spiritual dimension. Simply speaking, if there there are any ghosts at all running around out there, those seeking a unified theory of reality would have to go back to the drawing board.
I am a strong believer that this universe has a Creator, and that he created not only a physical dimension, but the spiritual as well. Further, I believe strongly that each of us possesses an eternal spiritual self, which in reality, is the essential, most important part of our natures. In fact, the existence of an eternal spirit would be one of the strongest indicators that God must exist. For if God doesn't exist, then all life, including homo sapiens, must have arisen by mere chance through a purely physical process. And if humans arose by such a process, how could such a mortal, temporal self give rise to an eternal spirit?
Those who are strict materialists therefore are quick to reject the existence of the human spirit. Any people claiming to have had out of body or Near-Death experiences, or who say they saw or interacted with long-deceased people or with spiritual reality in some way, have to be portrayed as quacks or hallucinators. In truth, while certainly many people must have made up stories for various motives, if even one account of a spiritual reality proved to be true, it would threaten and undermine the foundation of all materialism.
I say these things as someone who never has, to my own knowledge, ever seen or encountered a spirit. I think most people are in that category. However, does the fact that I never saw a spirit mean that they don't exist? Does the fact that I am blind, at least in a spiritual sense, mean that that the millions of people of throughout history who have this experience are all crackpots? To throw out the testimony of these multitudes of all races, cultures and ages would be a reckless act. Do you believe there is a spiritual dimension? Do you find reason to believe there is an eternal human spirit? Then you have a very good reason to believe in God.