Something that should probably come into play is that in Christ, death has been transformed. It does not mean the cessation of existence (it never did), nor does it mean annihilation or any such thing. My dear Lutheran pastor used to say "death is an active state -- dead people do not remain as they were when they were alive, only inanimate. They stink. They rot. They decay." So the soul (like the matter of the body) remains, but exists differently than it did before. This is true also for the soul moving away from God's love as opposed to being integrated into it. The promise of the resurrection is not that the soul endures forever. That happens whether we are united to Christ or not. For those outside of Christ, that is a curse instead of a blessing, because they spend eternity in the presence of God, but receiving His presence and even His love as torment. This is why, for example, we see Isaiah in the Old Testament fall down on his face in fear in the presence of God in His glory. To the one who is still in sin, God is received as terrifying instead of healing.
The promise in Christ is that our sins are remitted, our corrupted nature is healed, and we are able to be received into God's presence as united with Him, because we are united with His Son, who is of the same essence as the Father. Thus, it is not that the soul goes to one place or another, or is in one physical state of existence or another, but that the soul, which is to say, the person, perceives God differently when united to Him than when it is separated from Him by sin and self love.
Viewing the Fall in this light, it is much easier to see things as Mr. Erdner does. For Adam and Eve, the problem was not that they lost immortality in a fleshly sense, but rather that the source of life itself was He Whom they cut themselves off from by their rebellion.
