The common Christian teaching goes something like this: In the beginning, everything was perfect. Man lived in perfect relationship with God in the Garden and did not fear death. But then, man disobeyed, ate a piece of fruit, and "death entered the world."
The common Christian teaching...is not quite right.
This may surprise many, but death was present in the world before sin. At least, the Genesis record seems to indicate as much. Before sin, death was a possibility. The sin of the first man and woman made it only a guarantee.
See, there were two special trees in Eden - the Tree of the Knowledge of Good and Evil and the Tree of Life. Adam and Eve are commanded not to eat of the first, but they are given no commands regarding the second. Why? Because God always intended them to feast from the Tree of Life.
In fact, I think it's quite possible that Adam and Eve had already eaten of the Tree of Life, perhaps even multiple times, before they took a bite off the forbidden tree of knowledge.
How, then, did they die?
They stopped eating from it.
It seems too simple, or perhaps, too complicated. Would God really demand that His creation routinely eat from the Tree of Life in order to live forever? Of course He would! This is a God whose entire testimony is one of demanding constant faithfulness, repeated acts of worship. We pray, but we must keep praying. We tithe, but we must keep tithing. We read the Bible, but we must continue to read the Bible. We go to church, but we must continue to go to church. The entire sacred season is set up in calendars and rituals and festivals. We come to the Cross, but we must continue to carry our own Cross. Our God is a God of steady faithfulness, which requires not only that we do something, but that we keep doing something. (Some of this, of course, changed with Christ - baptism, for example. And that pesky little redemption thing.)
In the Old Testament, Israel brought sacrifices daily. Daily! It seems that even though the sacrifice sets your heart right with God, you must keep bringing it and keep setting your heart right or you will fall into trouble.
The same is true of the Tree of Life - men and women ate of it, but they must have continued to eat from it in order to live. They had to keep coming back. It's the way God's wired our hearts, and the way He planted His garden. Had Adam and Eve chosen not to eat from the Tree of Life, had they chosen to go too long without coming back to it, they would surely have died.
Just as we do when we stay away from God too long.
And that means that death was always possible, from the very beginning of creation. (And we know this, too, because creation continued to regenerate itself, and we know that new life requires death - the seed dies in order that the flower might grow.) The difference is that after sin entered the world, death became not a possibility, but a promise. God removed His people from the sacred space of the Tree of Life, that they might not be able to live forever a miserable life of knowing too much.
Although if you understand at all what I'm saying here about the Tree of Life, you understand, too, that whatever man came to know in that first sinful bite, he was destined to forget in short order....