Alma 42:6 - 42:10
Alma 42: 6 But behold, it was appointed unto man to die—therefore, as they were cut off from the tree of life they should be cut off from the face of the earth—and man became lost forever, yea, they became fallen man.
Now all men and women are subject to physical death. In which state they are no longer have access to the mortal experience. This is just like being cut off access to the Tree of Life. And since they cannot be mortal forever or regain the presence of God, they are cut off from any possibility of eternal life and are labeled “fallen men.”
Alma 42: 7 And now, ye see by this that our first parents were cut off both temporally and spiritually from the presence of the Lord; and thus we see they became subjects to follow after their own will.
The bottom line is that men are now cut off both temporally and spiritually from the presence of the Lord and are only subject to their own whims and desires.
Alma 42: 8 Now behold, it was not expedient that man should be reclaimed from this temporal death, for that would destroy the great plan of happiness.
Because men lose access to their bodies at death, the first phase of the plan of salvation was to allow men to regain their bodies after a period of time after death.
Alma 42: 9 Therefore, as the soul could never die, and the fall had brought upon all mankind a spiritual death as well as a temporal, that is, they were cut off from the presence of the Lord, it was expedient that mankind should be reclaimed from this spiritual death.
In addition, since man cannot become extinct, in other words, man intelligences and spiritual body cannot become be killed, something had to be in place to allow men to be able to regain God’s presence, otherwise they would wander through the eternities without any purpose or goals.
Alma 42: 10 Therefore, as they had become carnal, sensual, and devilish, by nature, this probationary state became a state for them to prepare; it became a preparatory state.
The purpose of mortality was to allow men to prepare for the life to come after the physical death. Life became a place to learn the lessons to prepare them for the life to come. However, mortality finds that most people become influenced by the lack of direct contact with God and become wrapped up in their own selfishness and easily influence by evil.