I suppose it depends on your interpretation of ?sprit?: if you see it as your conscious self, merely lacking in a physical manifestation (at least in our perceived dimensions), then it?s up to the individual whether they believe in heaven or hell or reincarnation. Although, I suppose that also depends on your interpretation of reincarnation, because if someone is reincarnated with what Syphonz called ?baby amnesia? one could debate whether YOU (as in your own conscious self) are reincarnated at all. The only possible way of getting round that problem would be to suggest that one?s self is not just conscious, but instead, the spirit is a type of energy, which is passed from generation to generation, with the current incarnation being unaware of the previous.
This leads me comfortably to what I think: I don?t believe in a existential conscience after death; I think when you die, that?s it for you as something that can directly influence others around you. However, the Platonic / Socratic concept of the preservation of intellect between interconnected generations is an intriguing prospect: I think that your actions in life echo in eternity (subtle film reference) through the people you have met and influenced. This idea also borrows something from the ancient Greek ?timé? (I think I?ve spelt that right), which means at the most fundamental level, that a warrior?s legacy is affected by their death; for example, in Homer?s The Iliad, Achilles has the option of dying on the battlefield and living for ever, or going home to his family and living to an old age with his lovey-dovey wife, before dying and loosing his existence in eternity.
We see alternating mixtures of the concepts of the eternal, the eternally contextual and the manifestation of ?the afterlife? all the time in stories: The Matrix, , Sunshine, Gladiator, Life of Pi, The Inferno, The Life and Opinions of Tristram Shandy, The Bible and zillions of poems. I suppose this is because it all ties in (in one way or another) with chaos theory and Dante?s ideas on the natural chaos of life being restored by hate and love; by acting in a certain way towards someone else, however subtle ? maybe you only say a few words to them in your entire life ? you affect them in one way or another, most likely at an unconscious level (I know that?s a bit of a cop-out, but if Freud can get away with, I can!).
Of course, the best bit about this ethos is its fundamental parallels with science, and more specifically thermodynamics, quantum mechanics and general relativity: The Conservation of Energy. Why can?t we expand this to include a conservation of ?spiritual? energy? (I know Einstein is probably turning in his grave, and all you physics undergraduates out there are trying to find the heaviest object to throw in my general direction, but this is fun, so I?m just going to run with it). I don?t mean conscious spiritual energy (i.e. that heaven and hell stuff), but with a large enough base of believers, one common idea can become ?alive? in the sense that it is pushed and pulled by enough interpretations to become almost conscious of its self. Some say the internet is beginning to display signs of this, in that is its own community of knowledge, which is divided up into sections much in the same way that the human brain assigns different areas for different tasks. Again, this is observed with the fractioning of belief systems like Christianity.
So. In death, your brain stops working, time becomes infinite to you and the natural level of degeneration that has been happening since you were born soars upwards until you cease to exist. But its up to you at the present whether you see this as a physical degeneration or a gradual watering down of the effects you had on others, until the human race ceases to exist.