The Savior said it, not me: baptism is a necessary prerequisite for entrance into the Kingdom of God. Yet it would be inconsistent to say that a loving God would send millions of His beloved children “to an endless hell” (Moroni 8:13) because they had not been baptized.
Because God loves all of His children, “He doeth not anything save it be for the benefit of the world” (2 Nephi 26:24). Therefore, everything God does is for the benefit of mankind and there is not anything that He does that is not for the benefit of mankind.
Because He wants us to be happy, he has provided a way for all of His children to receive salvation, “even as many as will” (Moses 5:9). For those who did not have the opportunity to hear the gospel and receive the saving ordinances that are necessary for salvation–baptism, for example–the Great Provider, even Providence, has provided a way. Baptism is necessary for entrance into the Kingdom of God. Baptism for the dead was revealed to the Prophet Joseph Smith so that souls might be saved. It is a service that is done for and in behalf of the dead so that they can enter into the Kingdom of God.
Baptism for the dead takes place in temples–sacred edifices that are consecrated as houses of the Lord. Baptismal fonts that are used in the temple rest on twelve oxen, usually carved out of stone or brass (shown). These twelve oxen represent the twelve tribes of Israel.
Baptisms for the dead are performed nearly exactly the same way for the dead as they are for the living. The only differences are the location (baptisms for the dead are performed in temples) and the person is doing as a proxy, or on behalf of the dead person. The dead person has the choice to either accept or reject the baptism. We just give them the ability to make that choice.
Baptisms for the dead are not peculiar to The Church of Jesus Christ of Latter-day Saints. Early Christians also understood the doctrine of and practiced baptisms for the dead. In the New Testament, Paul wrote, “Else what shall they do which are baptized for the dead, if the dead rise not at all? Why are they then baptized for the dead?” (1 Corinthians 15:29).
Paul is speaking to some groups of the Corinthians who did not believe in resurrection, yet still baptized for the dead. Paul is reproving these saints with this rhetorical question that shows that both resurrection and baptism for the dead are necessary principles in the gospel of Jesus Christ.
The love of God is not conditional. He loves us all, and would not deny salvation to those who seek it, even if they choose to seek it after this life. This is why baptism for the dead is performed in temples.