One of the big ideas from that series was affirming creation ex Deo ("from God") and ex nihilo ("from nothing"). The ground of all existence, as a positive expression of being, comes continuously from God. But as created, finite, and contingent being, we are called into existence from nothing. Thus, as I argued in my series, created existence is poised between God and nothing, and we move toward either one or the other.
I've been reading Augustine's The City of God, and in Book 14 I came across Augustine making this exact same argument in practically the exact same terms. Here's Augustine:
...But only a nature created out of nothing could have been perverted by a fault. That it is a nature, therefore, is due to the fact that it was created by God, but that it fell away from what it was is due to the fact that it was created out of nothing.
But man did not fall away so completely as to lose all being and cease to exist; rather, in turning to himself, he became less than what he was when he still clung to the one who supremely exists. Thus, to abandon God and to exist in oneself--that is, to be pleased with oneself--does not mean that one immediately loses all being but rather that one veers toward nothingness... (Book 14, Section 13)
That created nature is a nature, that it exists as something, "is due to the fact that it was created by God." Our positive existence comes ex Deo. But that created nature can fall and move away from God is "due to the fact that it was created out of nothing." When we move away from God we "veer toward nothingness."
Existing as we do between God and nothing, another thing I described in the "Theology of Everything" series is how the fall resulted in an "ontological drop" into contingency. Created being begins a drift toward non-being. Upon being separated from God, created being doesn't cease to exist but begins to suffer the effects of its contingency and finitude. Death, disease, decay, and damage come to shadow created being. As Augustine says here, when we abandon God we do not "immediately lose all being." Rather, we "veer toward nothingness."
That we continue to exist in being can only be due to being continually addressed by God. God does not permit our being to slide into non-existence. In pondering how Augustine describes this, here's a speculative take upon what all this might mean and look like.
According to Augustine, man falls and moves away from God when he "turns to himself." We "abandon God" to "exist in oneself." But what is this "self" we are turning to? Again, we exist ex Deo. That we have a self to turn to, a "nature," is due to the fact that we were "created by God." So in a sense, when we turn toward ourselves we aren't, strictly speaking, moving toward nothing. We are turning toward a positive, albeit contingent, existence--ourselves--which isn't a direct choosing of the void. Something in ourselves is a positive good and points back toward God. In choosing ourselves, therefore, we don't drop off an ontological cliff but create a kind of self-referential ontological knot, created being grasping at itself, which isn't choosing non-being but, being idolatrous, keeps us separated from God.
Something like this idea seems to be what Augustine is hinting at. We did not "fall away so completely as to lose all being and cease to exist." Rather we became "less than what we were." To "exist in oneself" and to "please oneself" does not mean we "immediately lose all being" but that we begin to "veer toward nothingness." It seems to me, putting these pieces together, that "choosing ourselves" isn't a total catastrophe. And my guess is that it's not a total catastrophe because there is, due to our existence being rooted in God, some positive good our ourselves. And that tether to goodness slows our slide into non-being. Something of God shines through created being, and that trickle of light slows our drift into non-being. But since we mistake created being for God our movement into nothingness continues.
Let me try to say all this more simply. In moving away from God we had two choices. Ourselves or nothing. Created being or the void. We chose ourselves. This was a choice between two evils, as both choices move us away from God. But in choosing ourselves, because our being comes from God, this choice was the lesser of two evils. Instead of jumping off an ontological cliff we chose a slow death.
