What might Preterism and Ultimate Reconciliation mean if they are both true? I offer a possible interpretation.
Preterism teaches that the end-time prophecies of the Old and New Testaments (including the book of Revelation) have already been fulfilled. If this is true, then the New Jerusalem is on earth now. Inside its gates lie The River of God and The Tree of Life. No darkness resides in it because God’s presence itself is light.
The gates of the New Jerusalem are always open, meaning that the blood of Jesus has provided access for all who want to enter. All sin has been atoned for. All have been given the gift of age-enduring (traditionally called eternal) life.
However, the whole earth isn’t in the New Jerusalem. Outside The Gates are those who haven’t (yet) believed The Truth.
Ultimate Reconciliation teaches that all will receive it, in due time. As children of the first Adam, we’re incapable of attaining The Kingdom on our own. (Most mortals don’t even know that.) The second and last Adam, Jesus, made the way and will eventually reveal it to everyone. Many don’t find out before they die, as we reckon it.
Those of the first Adam who do hear and receive the truth of the Gospel may enter The Kingdom now, not having to wait until death to attain it. To get in they must be born again of the Spirit from above. All New Life comes from above. No flesh and blood (i.e., descendants of the first Adam) may enter either in this life or the next. Only descendants of the last Adam, born from above (by The Spirit) may attain entrance either now or then.
Proper attire is required at the feast which those who live in the New Jerusalem partake. We must “put on The Lord Jesus Christ” to be accepted at The Table. Some proclaim a “gospel” where we aren’t required to change attire to enter. Since flesh and blood cannot enter—only what is born from above (of The Spirit) may enter—we must put on the attire of the righteousness of Christ, which comes through the new birth.