The stuff that has kept philosophers minds wrangled since day 0. I've melted a few brain cells myself contemplating such. What "is" existence? Surely 11 dimensional string theory is easier.

I'm reminded of a sci-fi novel named "Eon" by Greg Bear (wow, need to read that one again). One of the ideas in there is the ability to make a copy of yourself. They were useful for leaving behind to do something nasty and life risky while the primary safely escaped.

I think the biggest hurdle to humanity's future survival will be the temptation to make us our own gods as technology advances. In some ways that has already happened.

Then again, we may all just become Borgs.

Brian