“King Henry the Fifth! Thy ghost I invocate!”—Duke of Bedford, Shakespeare
An awful great deal has been made in virtually all spiritual belief systems out of the immaterial; the ghosts and spirits. In modernity, the concept has essentially grown to a matter of opinion, belief and so forth, whereby it is regarded more as some abstract conception vaguely surrounding a tactile reality, which can never be gotten after, behind, or be proven in any reliable manner—following convention—and so is just a matter of personal taste, imagination, upbringing, or what have you.
It seems worthy to note however, that, since the people living are the driving actors, the makers of and those that make up in its constituents the living realm, an abstraction of this kind has some manner of physical manifestation. Arguably, if one’s spirit would be about that which is "a part"—so to say—of one’s physical embodiment, the very conception of this one individual in the minds of others, their memory, their impression, is what creates the abstract presence of a "ghost," "soul," or "spirit."
Exactly so, the Duke of Bedford did exclaim in the opening scene of Shakespeare’s Henry VI, where after the aforementioned quotation he prompted to say: “Prosper this realm, keep it from civil broils!” For, in praise of Henry VI, the Duke of Bedford held the impression of his characteristic particularity in such esteem; he figured it be proper to ascribe a peaceful quality to his person, doing so based on the recollection, the impressed conception, of the King’s previous physical behavior.
So, this brings along with itself that one’s personal conception of ghosts and spirits influences the way in which they prevail. For if you conceive of them as an incomprehensible abstract realm apart from the physical world in some way, but that you do not know how exactly, you may well project things of ghostly nature to that which you in the physical realm similarly do not understand. As such, it becomes that ghosts and spirits are—by the driving living actor—solely projected, and so creatively born into reality, through his fears, by virtue of his confusion. Whereas, if you conceived of them as simply that which lies apart from the bodily appearance of one, you can carry forth this spirit in a different way; immortalizing its characteristic particularities! Even denying the existence of a spirit becomes itself the way in which it takes physical form, for it is the manner in which the spiritual realm lives through physical behavior; denial is only its admission—however, arguably less fun.
It happens to be so that in the age of modern science, and typically a-religious societies, what is inexplicably indescribable becomes what is conventionally considered "unearthly," or so, "ghostly." This same fundamental confusion fails to recognize that, beside there being such a thing as an abstract immaterial realm apart from the physical material world, it could only exist by virtue of its relationship to the physical material world. For without material, there can be no immaterial, and vice versa. So it is, that in being taught airy ghostly concepts, without sturdy connection to their physical ground, one never comes to see how the two are not only harmoniously compatible, but in all actuality, truly inseparable and require each other to exist. The material realm is not the puppet of some unknown vastly powerful immaterial realm, neither be it the other way around; they exist through one another. So too, are ghosts not simply unearthly as conventionally regarded. That is, at least, if one were to realize it.