I wouldn't want to live on after everyone I love died.

OK, now when I look back on how I behaved, how I thought about the world, the "me" who inhabited my head twenty years ago, the perspective is so very different that it's almost like having a stranger in my head.

Now imagine that same self-alienation, that radical change in the self, only extended over a period of two hundred years instead of twenty. It's just . . . too odd to consider.

What about social cohesion? There's a certain social and cultural differentiation that takes place as a natural result of aging. Eighty-year-olds typically find it hard to relate to teenagers and early-twentysomethings. What happens when we have four or five hundred year olds walking around? What kind of common grounds are they going to have with the rest of society?

I'm not sure about immortality but I wouldn't mind a few extra years. I'm in my fifties now and while I love my life, I'm always cognizant of the fact that I've only got about thirty to forty years left on this wonderful green planet. I'm not upset about the idea of dying but I'm still a little annoyed that I won't get to see the end of the movie and find out how it all ends.

I've always been in favor of death. If we didn't have it to shake things up, the world would become static in a bad way.

I fear death but immortality is not something I'd ever opt for, particularly since I am increasingly aware that bodies break down in an irrevocable way over time. (And I don't want to hang around indefinitely hoping that science fixes that.) Not to mention how lonely it would be.

I guess I'd pick 45 as a pretty great age . . . old enough to have some wisdom, body still in decent shape, a big farther from death than I am now. Like octothorpe I am a lot more conscious of the ticking clock now that I am in my mid fifties.

Well, the thought of my life as it is going on forever would be greatly disturbing for me, but immortality would give a person the chance to try so many things that I can see the attraction there. Sort of. Maybe.

I think 40 would be a good age if I had to pick. Still healthy and fit enough not to be held back by physical limitations, but smart enough to survive.