Mormonism and polygamy/Requirement for exaltation
Plural marriage as a requirement for exaltation
Important introductory material on plural marriage available here
Joseph Smith era:
Doctrine and Covenants and Church History Seminary Teacher Manual: "Do not speculate about whether plural marriage is a requirement for the celestial kingdom"
Doctrine and Covenants and Church History Seminary Teacher Manual, LESSON 140:
Do not speculate about whether plural marriage is a requirement for the celestial kingdom. We have no knowledge that plural marriage will be a requirement for exaltation.
Gospel Topics: "During the years that plural marriage was publicly taught, all Latter-day Saints were expected to accept the principle as a revelation from God"
Gospel Topics on LDS.org:
During the years that plural marriage was publicly taught, all Latter-day Saints were expected to accept the principle as a revelation from God. Not all, however, were expected to live it. Indeed, this system of marriage could not have been universal due to the ratio of men to women. Church leaders viewed plural marriage as a command to the Church generally, while recognizing that individuals who did not enter the practice could still stand approved of God. Women were free to choose their spouses, whether to enter into a polygamous or monogamous union, or whether to marry at all. Some men entered plural marriage because they were asked to do so by Church leaders, while others initiated the process themselves; all were required to obtain the approval of Church leaders before entering a plural marriage.
Charles W. Penrose (Improvement Era): "it is not stated that plural marriage is thus essential"
Charles W. Penrose in the September 1912 Improvement Era:
Question 4: Is plural or celestial marriage essential to a fulness of glory in the world to come?
Answer: Celestial marriage is essential to a fulness of glory in the world to come, as explained in the revelation concerning it; but it is not stated that plural marriage is thus essential.
Question: Did early Mormon leaders teach the plural marriage was a requirement for exaltation?
Some 19th century Church leaders taught that plural marriage was a requirement for those wishing to enter the highest degree of the celestial kingdom
To obey the Lord's commands in all things is necessary for exaltation. (Our inevitable failure to live perfectly requires the grace of Christ's atonement.) Members of the Church in, say, 1860 who refused to follow the counsel of prophets and apostles put their spiritual standing in jeopardy. Likewise, members who refuse to obey present counsel are at risk.
Question: Because Mormons do not currently practice plural marriage, does this mean that early leaders who taught that is was required were wrong?
The purpose of modern prophets is to give the Saints the will of God in their particular circumstances
Critics of the Church ignore that the purpose of modern prophets is to give the Saints the will of God in their particular circumstances. Joseph Smith wrote specifically of the issue of plural marriage:
This is the principle on which the government of heaven is conducted—by revelation adapted to the circumstances in which the children of the kingdom are placed...in obedience there is joy and peace unspotted, unalloyed; and as God has designed our happiness—and the happiness of all His creatures, he never has—He never will institute an ordinance or give a commandment to His people that is not calculated in its nature to promote that happiness which He has designed, and which will not end in the greatest amount of good and glory to those who become the recipients of his law and ordinances. 
LDS doctrine also holds that the prophet, when speaking in an official capacity, speaks on behalf of the Lord:
whether by mine own voice or by the voice of my servants, it is the same. (DC 1:38)
Critics of the Church often come out of an inerrantist background, or draw on arguments first formulated by religious inerrantists or fundamentalists. In an inerrantist religion, God's instructions cannot change with circumstances—if they did, then the Biblical record would not be sufficient, on its own, to guide us. Since inerrantists require, above all, that the Bible be the sole authority, they must assume that God's requirements are always the same.
However, even the Bible gives many examples of God giving new instructions because of new circumstances, or contravening previous instructions:
- Noah (but no other prophet) was to build an Ark (Genesis 6:14)
- Moses implemented the Passover, which was hitherto unknown (Exodus 3:12-28)
- Jesus revoked the celebration of Passover, and modified the ordinance and its performance at the Last Supper (Matthew 26:26, Mark 14:22, Luke 22:19)
- Hosea was commanded to marry a prostitute as a sign to Israel Hosea 1:1-3
- Jesus told his disciples only to preach to Israelites (Matthew 10:5-6, Matthew 15:24)
- The Lord later told the prophet (Peter) to preach to all people (Acts 10:14-28)
In each case, failure to obey carried significant penalties. Yet, when proper authority altered or rescinded a command, spiritual disaster followed those who did not obey the new instructions.
President John Taylor said:
Where did this commandment come from in relation to polygamy? It also came from God. It was a revelation given unto Joseph Smith from God, and was made binding upon His servants. When this system was first introduced among this people, it was one of the greatest crosses that ever was taken up by any set of men since the world stood. Joseph Smith told others; he told me, and I can bear witness of it, "that if this principle was not introduced, this Church and kingdom could not proceed." When this commandment was given, it was so far religious, and so far binding upon the Elders of this Church that it was told them if they were not prepared to enter into it, and to stem the torrent of opposition that would come in consequence of it, the keys of the kingdom would be taken from them. When I see any of our people, men or women, opposing a principle of this kind, I have years ago set them down as on the high road to apostacy, and I do to-day; I consider them apostates, and not interested in this Church and kingdom. 
Question: If early Church leaders taught that plural marriage was required, does this mean that current members are not capable of achieving exaltation?
There is no doctrine in the Church that states that plural marriage is the norm, or that it is something that will be required for exaltation
The fact that the modern Church does not approve of or practice polygamy does not mean that present members of the Church believe that the principle of plural marriage is false—rather, they believe that it is a principle only to be practiced when the Lord commands it for His purposes.(See Jacob 2:27-30.) There is no doctrine in the Church that states that plural marriage is the norm, or that it is something that will be required for exaltation.
To see citations to the critical sources for these claims, click here
- "LESSON 140: Doctrine and Covenants 132:1–2, 34–66," Doctrine and Covenants and Church History Seminary Teacher Manual, 488 (2013).
- "Plural Marriage and Families in Early Utah", Gospel Topics (2013)
- "Peculiar Questions Briefly Answered," Improvement Era 15:11 (September 1912)
- Joseph Smith, History of The Church of Jesus Christ of Latter-day Saints, 7 volumes, edited by Brigham H. Roberts, (Salt Lake City: Deseret Book, 1957), 5:135. Volume 5 link
- John Taylor, "Our Religion Is From God," (7 April 1866) Journal of Discourses 11:221.