A friend of mine were having an argument about whatever, and as is usual, it comes down to the essence of reality. His point, which is more/less the allegory of the cave (as I understand it), was that since everything we can experience and know is brought to us by our perceptions, then when we die, or cease to perceive, all of reality goes away with it.. or at least, there is no way to prove otherwise.
Basically, all you really KNOW is that you can 'think'.. the rest is just a guess. Even your physical body might not be as you think it is (a-la The Matrix or something), let alone the World. So once your consciousness is gone, you can never say with 100% accuracy that anything else will continue to exist. This isn't necessarily a bold statement in itself, but it has bigger implications, such as there is no way to be 100% certain of Religion, etc.
I've been trying to grapple with this for some time, but can't come up with any other/better way of looking at things. I've also attempted to explain this as best I could, but it's late so please ask if clarification is needed.