On "Death"

Have you ever pondered on the issue of "death"?  Tonight, a group member presented his views on this topic.  He took a personal approach instead of a theoretical one.  At the age of 12, when he was on the way to a movie, he witnessed a serious accident, in which a middle-aged woman was hit at the head by a falling street lamp post.  He didn't saw the actual action but the scene was terrible enough: the woman lying on the ground with her skull cracked open and part of her brain exposed.  At that moment, he knew what terror really was.  When he grew up, he graduated from a seminary and became a church pastor, though he eventually quitted.  He had witnessed many times old parents of Christian children resisted conversion life-long and yet yielded and received baptism towards the ends of their lives.  In his opinion, old failing parents subcribe to their children's Christian religion because they want their children to feel better---with a hope to "see again in heaven". 

"Death" is a big topic that always fascinates me.  I am my brain.  Physical damage or disruption of its energy supply (glucose and oxygen) causes my "death".  Biology has listed several characteristics of life such as organization, energy use, homeostasis, responsiveness, growth, and reproduction.  But living organisms can be understood as complex molecular machines, ie, they can be just moving "non-living" structures.  Is virus living or non-living?  The line between living and non-living can be vague.  What is so fearful to cross the vague line to the other side?  Perhaps "fear" is actually the instinct of living structures to stay alive.