Mormons believe that vicarious baptisms give the deceased, who exist in the afterlife as conscious spirits, a final chance to join the Mormon fold, and thus gain access to the Celestial Kingdom. To Mormons, only members of the LDS priesthood possess the power to baptize.
“It doesn’t matter if you’re a Baptist or a Buddhist,” said Kathleen Flake, a Vanderbilt University scholar who has studied the church, “it’s about who has the authority to perform the sacrament.”
Flake said Mormons are encouraged to baptize at least four generations of forebears to seal the family for eternity. So the LDS church has built the world’s most extensive genealogical library in Salt Lake City with 700 employees and more than 2 billion names.