Is it because of the pain? Do we think that death will be even more painful than the worst pain we can imagine? I'm not so sure this is it. Logically, it's much, much more painful to be alive than dead. And dying often seems slow and painful but even more often seems quick. People who die in a car accident might not even feel anything because the events happen so quickly. Yet we do fear dying in a car accident, or being shot in the head, or other quick ways to die.
Do we fear death because of the change? Do human beings just naturally fear drastic changes, death being the most drastic of them all?
Or is it because what comes after death is a complete mystery? No one really knows what happens after death, and humans do have a tendency to fear the unknown. Anything could happen after death- we might find ourselves in the Christian Heaven, or back on earth as a reincarnation, frozen in time, or in a completely new dimension. Will it be like sleep? Will we be alone, or with other beings who have passed on? But even people who think they know exactly what happens still fear death. Maybe they are not as sure of their beliefs as they claim to be, or maybe they are afraid for a different reason.
Maybe it's because no one knows exactly how much of ourselves die when our bodies die. People speak of a "soul" that lives on after our bodies die, but what is a soul, really? Does a soul have thoughts even after all neurologic activity ceases in our brain? Do we carry our memories with us? Will we be able to feel any pain or emotion despite having no nerve cells? Will we have the ability to make decisions, free will? Will we have any awareness at all?
What about you? Do you fear death, and if so, why?