When individuals or groups of people turn away from the principles of the gospel, they are in a state of apostasy. One example is the Great Apostasy, which occurred after the Savior established His Church. After the deaths of the Savior and His Apostles, men corrupted the principles of the gospel and made unauthorized changes in Church organization and priesthood ordinances. Because of this widespread apostasy, the Lord withdrew the authority of the priesthood from the earth. This apostasy lasted until Heavenly Father and His Beloved Son appeared to Joseph Smith in 1820 and initiated the restoration of the fulness of the gospel.
During the Great Apostasy, people were without divine direction from living prophets. Many churches were established, but they did not have priesthood power to lead people to the true knowledge of God the Father and Jesus Christ. Parts of the holy scriptures were corrupted or lost, and no one had the authority to confer the gift of the Holy Ghost or perform other priesthood ordinances.
We now live in a time when the gospel of Jesus Christ has been restored. But unlike the Church in times past, The Church of Jesus Christ of Latter-day Saints will not be overcome by general apostasy. The scriptures teach that the Church will never again be destroyed (see D&C 138:44; see also Daniel 2:44).
Although there will not be another general apostasy from the truth, we must each guard against personal apostasy by keeping covenants, obeying the commandments, following Church leaders, partaking of the sacrament, and constantly strengthening our testimonies through daily scripture study, prayer, and service.
—See True to the Faith (2004), 13–14
"Whither the Early Church?"
S. Kent Brown, Ensign, Oct. 1988, 7–10
Why did the early Christian Church fall into apostasy?
"Early Signs of the Apostasy"
Kent P. Jackson, Ensign, Dec. 1984, 8–16
The New Testament both prophesies and documents the first-century apostasy.
"The Message of the Restoration"
Charles Didier, Liahona, Nov. 2003, 73–75; or Ensign, Nov. 2003, 73–75
There came a time during the great Apostasy when the religious quest surfaced again—the "Why is it so?" which led to the Restoration.
"Apostasy and the Restoration"
Dallin H. Oaks, Ensign, May 1995, 84–87
In the process of what we call the Apostasy, the tangible, personal God described in the Old and New Testaments was replaced by the abstract, incomprehensible deity defined by compromise with the principles of Greek philosophy.
"Apostasy, Restoration, and Lessons in Faith"
Andrew C. Skinner, Ensign, Dec. 1995, 25–31
We affirm that the Apostasy and the Restoration occurred just as foretold. Both offer us lessons in the importance of following the Savior's chosen leaders.
M. Russell Ballard, Ensign, Nov. 1994, 65–67
The New Testament indicates that the early Apostles worked hard to preserve the church that Jesus Christ left to their care and keeping, but they knew their efforts would ultimately be in vain.
"From the Beginning"
Neal A. Maxwell, Ensign, Nov. 1993, 18–20
New Testament epistles clearly indicate that serious and widespread apostasy—not just sporadic dissent—began soon after the deaths of the Apostles.
Guide to the Scriptures
"Preventing Personal Apostasy"
Teachings of Presidents of the Church: Brigham Young, Chapter 12
"How Do Mormon Beliefs Differ from Other Christians?"
A video clip of Elder M. Russell Ballard addressing this question.
Encyclopedia of Mormonism
(Please note that the contents of the Encyclopedia of Mormonism, a joint product of Brigham Young University and Macmillan Publishing Company, do not necessarily represent the official position of The Church of Jesus Christ of Latter-day Saints.)
"The Church of Jesus Christ in Former Times"
Gospel Principles, Chapter 16
"Be Not Deceived, but Continue in Steadfastness"
Doctrine and Covenants and Church History Gospel Doctrine Teacher's Manual, Lesson 24