This is another of the most-quoted verses in the entire Book of Mormon. It sums up the reason for “the Fall”: Adam and Eve did what they had to do in eating the fruit so that other human beings could have life. Mormons believe that every individual who has ever lived has an immortal soul, or spirit, that existed and even made important choices before this mortal life.
In Mormon theology, all spirits have to experience the probationary state of mortality in order to prove their worthiness and mature enough to receive Christ’s atonement and eventually return to God in heaven. No spirit can do this, though, without a physical body, despite its limitations, illnesses, and temptations.
So Adam and Eve—as we are told in verse 25 with admirable economy—fell that we might “be,” or have the blessing of a mortal existence. Moreover, the verse reveals the basic reason why human beings exist: to have joy. Mormons believe true joy arises from coming to understand who we are as God’s children and learning to follow his teachings.