Back in high school, a good friend of mine and I often discussed religion. He came from a strongly Catholic family, and for a long time had been a staunch defender of faith among our group of friends. Gradually, though, his inquisitive mind allowed doubts to creep in, and he slowly turned to agnosticism.
I was discussing something with him one day, when I brought up my ideas about an afterlife:
I told him that I could not concieve of an end to myself, and so didn't it seem natural to assume an afterlife?
He responded that he'd thought about it, and he didn't think something as tenuous as conciousness could be expected to continue. Every night, we lose conciousness and cease to exist (as we think of it) for hours at a time. Why would conciousness, which fails to survive in a huge chunk of our biological lives, be any more robust after death? The brain's and body's functions slow during sleep, and slow to a stop in death. Why should the effects be so much different in two events that ultimately differ only in scale?
My argument, I have since realized, holds very little water. But his... It's not an airtight argument against an afterlife, nor does it claim to be. However, the reasoning is impeccable. Undeniable.
I was sincerely bothered by this thought. And not just at the time, it continued to bother me all through my mission, after coming home, and basically up to the point in time that I abandoned faith entirely.
I still can't argue with it. It is not conclusive, but it sure makes it seem likely that conciousness is not retained in death.
Why do we want so badly to escape death? It is unknown, I guess. We cling to existence because that's all we know. Nobody can remember their first moment of being, can they? Memories just kind of... fade back in time. No beginning. So we try to conclude that nonexistence is not actually a state we are capable of achieving, because we have no concept of nonexistence, and it terrifies us.
Now it is late at night, and I must go die for a while.