In Mormonism, the preexistence (or premortal existence) refers to life before birth. Mormons believe all people lived as literal spirit children of Heavenly Father and Heavenly Mother in a premortal realm. In this state, spirits were taught, grew in knowledge, and prepared for life on earth.
Central to the preexistence is the “council in heaven,” where God presented his plan of salvation. Jesus accepted the plan, offering himself as Savior, while Lucifer rebelled and was cast out with his followers. Spirits who supported Jesus received the opportunity to be born on earth, keep commandments, and progress toward exaltation.
This teaching emphasizes agency: mortality is a test to see if people will choose God’s plan and prove worthy of eternal life with him. Some Mormons also believe the level of faithfulness in the preexistence influences circumstances in this life (such as being born into an LDS family).
Biblical Christianity, however, does not teach a premortal existence. The Bible presents human life as beginning at conception, not as spirit children of heavenly parents (Psalm 139:13–16; Zechariah 12:1). Our hope is not in proving our worth from a past life but in the new life God gives us through Christ.