This post-Eden/pre-atonement state provides two conditions. First, human beings can “follow after their own will.” This power results from eating the fruit of the tree of knowledge of good and evil, which bestowed agency (the ability to distinguish good and evil and make choices) on Adam and Eve. These choices have meaning because they have eternal consequences. (See commentary accompanying 2 Nephi 2:11–12.)
The price of choice, however, is the possibility of sin. When Alma suggests that it was “not expedient that man should be reclaimed from this temporal death, for that would destroy the great plan of happiness,” he is commenting on the prohibition of eating from the tree of life. Still not commenting yet on the atonement, he is repeating his previous argument that Adam and Eve were forbidden to eat of the tree of life; if they had not eaten, they would have lived forever in their sins, a condition that would deny any value to their existence.