In a short book discussing Jesus’ final hours before his sacrificial death, W. Jeffrey Marsh wrote the following about our fate if Christ did not atone for our sins:
OUR FATE WITHOUT CHRIST
Have you ever wondered what our fate would have been had the Savior not completed the Atonement? The Fall is so powerful that it has dominion over all. By itself, it would have destroyed the plan. “Wherefore, the first judgment which came upon man [the physical and spiritual death that came as a result of the Fall] must needs have remained to an endless duration” (2 Nephi 9:7). Without the resurrection, we would have remained as unembodied spirits forever. And without the Savior’s atonement, we could never have become cleansed from sin. We would have been unclean spirits throughout all eternity—precisely what Satan is (2 Nephi 9:12-13). That is why Alma taught, “It is expedient that an atonement should be made, for according to the great plan of the Eternal God there must be an atonement made, or else all mankind must unavoidably perish” (Alma 34:9). Little wonder Nephi cried out: “O the wisdom of God, his mercy and grace! . . . .O how great the goodness of our God, who prepareth a way for our escape from the grasp of this awful monster; yea, that monster, death and hell, which I call the death of the body, and also the death of the spirit . . . O how great the plan of our God!” (2 Nephi 9:8, 10, 13).
All that Christ passed through for us in his final hours will one day cause every knee to bow and every tongue to thank him for the Atonement and to thank Heavenly Father for the great plan of salvation. (W. Jeffrey Marsh, His Final Hours [Salt Lake City: Deseret Book, 2000], 15-16, emphasis in bold added)
The portion in bold stood out for me while reading this book today, as it shows that there are modern Latter-day Saint authors who (correctly) note that the Fall was not a completely positive occurrence; instead, a considered Latter-day Saint view would be similar to the “felix culpa,” a view that even Augustine held to:
"For God judged it better to bring good out of evil than not to permit any evil to exist." - Augustine, Enchiridion On Faith, Hope, and Love, VIII
One should read D&C 29 where Adam/Michael is royally chewed out by God for the Fall. Such is a great contrast to the folk doctrines about the Fall that permeate a lot of Latter-day Saint works.
