Essence: the properties or attributes by means of which something can be placed in its proper class or identified as being what it is. (Webster's)

Thus, the assertion that differentiation of the actual from the from the virtual is essential is based upon the supposition that they possess fundamentally different attributes which define them. Pragmatically, we know this to be true. We know that virtual space is not actual space, and we know this by experience. When we see a virtual apple and an actual apple, while we may claim that both are real, we know that the actual apple is real in a different sense; that is, in essence. While "essence "is a problematic distinction, a distinction was necessary, and due to the complexities and limitations of language, this is the distinction that was least problematic for this discourse. The use of the term "essence" is not meant to evoke Plato or Aristotle, it is meant a linguistic device to enable this discussion.