Derech Hashem – The Way of G-d 2:4:2
Adam and Eve — who were everyone’s ancestors, of course 1 — were on a far greater spiritual level than any one of us, as we’d already explained 2. They deserved great homage and eternal life, and had they not sinned they’d have achieved greater and greater heights 3.
They’d then have had as many descendants as G-d saw fit for there to be, and they’d have all delighted in His benevolence along with Adam and Eve. It’s just that those descendants were to be comprised of different levels in that some would have been primary and others secondary, “roots” and “branches” 4.
But Adam and Eve descended far downward when they sinned and became sullied with all sorts of murkiness and impurity, as we’d also pointed out 5. As a consequence their descendants – we ourselves — slid to a level that almost precluded them from reaching the exalted and immortal level originally due them.
That’s not to say that we’re incapable of ascending higher than the level we’d sunk to, or that Adam and Eve were denied the chance to return to their original level even though they’d descended so. Humanity has been granted the freedom to choose to ascend to a very great level. It’s just that there’s a time limit within which we can do that, not unlike the time limit each one of us has in this world to rectify ourselves and attain a place in the World to Come 6; after all, everything that requires effort has a time limit.
1 This point will matter later on when it’s explained why the Jewish Nation alone was chosen.
2 See 1:3:6-8.
Ramchal depicts them in Adir Bamarom (p. 29) as being so pure at first that they could have single-handedly finished off the order of perfection that G-d set in motion. All wrong would have been turned to right there and then, as will eventually happen, and all of creation would have been utterly purified.
3 See 1:3:13 for our connection to that, and Da’at Tevunot 40, 126 for more about their sin.
4 I.e., major family lines and minor ones.
5 See 1:3:8 and 1:4:2.
6 See 1:3:3.