Except that in Buddhism, this is not a belief system, but
something that is observable and experience-able for anyone who
investigates according to Buddha's instructions. Therefore, it is
actually a science, but it is spiritual science... not 'material
science'. It concerns the individual's experience.
Nirvana is also not an after-life thing, but something
actualize-able, attainable, experience-able this very life. And
many people have experienced it, in the past, and also now.. even
some in sgforums.
In Buddhism, we teach that 'eternalism' and 'nihilism' are extremes
-- notions of 'eternity' and 'annihilation' does not exist for an
enlightened being, because he has eradicated the view that he is a
separate, permanently existing self.