Claim. The human spirit can grow only while it abides in the flesh — earthly life is the irreplaceable soil for spiritual maturation. After death, all the qualities of the spirit are already developed; sinful conduct on earth aggravates evil in the spirit, while redemption granted on earth opens the way to becoming good. This is why Jesus had to come in the flesh, and why the primary objective of the providence of restoration must be carried out on earth.
Elaboration. Per 6.3.2. The Structure and Functions of the Spirit Self: “The spirit can grow only while it abides in the flesh. Thus, the relationship between the physical self and the spirit self is similar to that between a tree and its fruit… It can be inferred from the above that the spirit self can attain perfection only during a person’s earthly life.”
The eschatological consequence: “only when a person reaches perfection… while on earth can he fully delight in the love of God as a spirit after his death… Sinful conduct during earthly life aggravates evil… while the redemption of sins granted during earthly life opens the way for his spirit to become good.”
The christological corollary: “This was the reason Jesus had to come to the earth in the flesh… Jesus gave the keys to the Kingdom of Heaven to Peter… because the primary objective of the providence of restoration must be carried out on the earth.”
This is DP’s structural reason for rejecting salvation-by-post-mortem-purgation. The spirit world depends on earthly events for its own resolution — ancestors-in-spirit cannot complete their growth without descendants-in-flesh. Earth is theologically central; heaven is derivative.