Funny, I remember responding to this thread a few weeks back. But now that I really think about it, it was within a highly lucid dream and I vaguely recall not finding the right words or something like that. And I truly appreciate all of the fine ideas presented within this intriguing thread. Such intelligent insights!
Anyway, I firmly believe that Heaven exists, as does Purgatory and Hell. I see these as bands of conscious-awareness (or strings, if you will). Our perceptual capacity includes ascending to Heavenly planes of Being, as well as sinking into the depths of Hell states. Not just psychically but materially, as well. Any sensitive person would have to agree that Heaven and Hell can be found amongst humanity's collective experience. Unlike within the "animal kingdom" (of which we are an intricate part), the human species rationally observes these dichotomies. We subjectify our passing flow of experiences and question their reality. Entheogens simply amp this innate human process.
But if the OP meant is there a Heavenly plane above all others, the seat of Supreme Gnosis... this is another thing, altogether. Such a "Heaven" would be Omniscient, objective and beyond the grasp of us mortal folks. Or is it? It may just be that such an inter-phase is our natural and destined, next step in expanding our Atmic awareness. Many of us have shifted our attention upon such realms and touched something so far beyond words it behooves us to silence our minds and reflect it's effulgence.
So, all semantics aside, there surely exists a plane of being which is Heavenly. The ancient Zoroastrians described this level as Paradise. I has been called Anaami by the Sikhs. and while quite a universal concept, it is shaped uniquely to the culture which envisions it's reality.
I personally believe that deep within the Inner Light, exists a portal to such a dimension of existential being. A vortex of emptiness, like a "black hole" within the blinding effulgence, if you will? It is in a sense, a passage way of sorts and our souls are able to partake of an immersion within it's insubstanciality. These peak eclipsings are sheer Nirvana to immerse oneself within, as many of you good people have experienced many times.
I liken Heaven to
The White Void. The Tibetans made reference to this axiom The Clear Light of the Void. We are all potentially able to shift our awareness enough to traverse deeper into his vortex and in so doing, transcend our separation from this Heavenly Field. Yeah, I see Heaven as the Unified Field of Being. And while human words are just symbolic gestures to crystallize something quite ineffable and insubstantial... they are certain aspects we can discuss reasonably, hypothetically and even religiously.
That being said, I do not feel that Heaven is something sequential or that our existence is on a linear, ascending track, a "Stairway to Heaven" into higher and higher realms (leaving the material self behind forevermore). It may be on one level, sure but if such a higher plane is truly Heavenly, it would be immanent upon all planes, all levels and accessible from all frequencies of thought (if one but look beyond appearances and circumstances).
I honestly think this is one of the greatest illusions which we dream, that we are somehow separate from the Heavenly frequency of conscious-awareness. I also believe that Heaven is the true nature of all things, albeit temporarily hidden from our temporal view, nestled centrally within the core of reality, beneath all of it's seeming appearances.
There is no self to which I cling, for I am one with everything.