Chapter 8: The Fall, D: The Fall Was a Purposeful Step in God's Plan of Salvation

The fall was a necessary and planned part of life on Earth. It was not an accident, nor an arbitrary punishment. God designed that fall should bring about our fallen state, which was necessary for our eternal development.

We came into this world to die. That was understood before we came here. It is part of the plan, all discussed and arranged long before men were placed upon the earth. When Adam was sent into this world, it was with the understanding that he would violate a law, transgress a law, in order to bring to pass this mortal condition which we find ourselves in today.
Smith, Doctrines of Salvation, 1:66

When Adam was driven out of the Garden of Eden, the Lord passed a sentence upon him. Some people have looked upon that sentence as being a dreadful thing. It was not; it was a blessing. . . .
In order for mankind to obtain salvation and exaltation it is necessary for them to obtain bodies in this world, and pass through the experiences and schooling that are found only in mortality. . . .
The fall of man came as a blessing in disguise, and was the means of furthering the purposes of the Lord in the progress of man, rather than a means of hindering them.
Smith, Doctrines of Salvation, 1:113-14

Did they [Adam and Eve] come out in direction opposition to God and his government? No. But they transgressed a command of the Lord, and through that transgression sin came into the world. The Lord knew they would do this, and he designed that they should.
Brigham Young, Discourses of Brigham Young, 103

We needed to be tempted by Satan in order to truly have free agency. If all we know is good, we don't really have a choice, and thus, no agency. With temptation also came the ability to know the joy that comes from choosing good over evil.

And it must needs be that the devil should tempt the children of men, or they could not be agents unto themselves; for if they never should have bitter they could not know the sweet--Wherefore, it came to pass that the devil tempted Adam, and he partook of the forbidden fruit and transgressed the commandment wherein he became subject to the will of the devil, because he yielded unto temptation.
D&C 29:39-40

Adam fell that men might be; and men are, that they might have joy. And the Messiah cometh in the fulness of time, that he may redeem the children of men from the fall. And because that they are redeemed from the fall they have become free forever, knowing good from evil; to act for themselves and not to be acted upon, save it be by the punishment of the law at the great and last day, according to the commandments which God hath given. Wherefore, men are free according to the flesh; and all things are given them which are expedient unto man. And they are free to choose liberty and eternal life, through the great Mediator of all men, or to choose captivity and death, according to the captivity and power of the devil; for he seeketh that all men might be miserable like unto himself.
2 Nephi 2:25-27

If we cannot be good, except as we resist and overcome evil, then evil must be present to be resisted.
So this earth life is set up according to true principles, and these conditions that followed the transgression [of Adam] were not, in the usual sense, penalties that were inflicted upon us. All these . . . that seem to be sad infliction of punishment, sorrow, and trouble are in the end not that. They are blessings. We have attained a knowledge of good and evil, the power to obtain redemption and eternal life. These things had their origin in this transgression. The Lord has set the earth up so we have to labor if we are going to live, which preserves us from the curse of idleness and indolence; and thou the Lord condemns us to death-mortal death-it is one of the greatest blessings that comes to us here because it is the doorway to immorality, and we can never attain immorality without dying.
So these are all real blessings. We come to earth with all these condition arranged as they are so that we have to struggle constantly against evil, struggle to preserve our lives, struggle for everything of true value-that is the thing for us to understand-this is the course of life that is most desirable, and for our good. We have no need to find fault with these conditions. The Lord has ordained them all for our welfare and happiness.
Morris, in Conference Report, April 1958, 39

If the fall had never happened Adam and Eve would never had had children. It was not a matter of everyone living happily in the garden of Eden, for nobody would ever have been born. The fall was necessary for mankind to come upon the earth in the current state.

And now, behold, if Adam had not transgressed he would not have fallen, but he would have remained in the garden of Eden. And all things which were created must have remained in the same state in which they were after they were created; and they must have remained forever, and had no end.
And they would have had no children; wherefore they would have remained in a state of innocence, having no joy, for they knew no misery; doing no good, for they knew no sin.
But behold, all things have been done in the wisdom of him who knoweth all things.
2 Nephi 2:22-24


And in that day Adam blessed God and was filled, and began to prophesy concerning all the families of the earth, saying: Blessed be the name of God, for because of my transgression my eyes are opened, and in this life I shall have joy, and again the flesh I shall see God.
And Eve, his wife, heard all these things and was glad, saying: Were it not for our transgression we never should have had seed, and never should have known good and evil, and the joy of our redemption, and the eternal life which God giveth unto all the obedient.
Moses 5:10-11