This article deals primarily with pre-existence per se, as opposed to the pre-existence of Christ.
Pre-existence (also spelled preëxistence), beforelife, or pre-mortal existence refers to the belief that each individual human soul existed before conception, and at conception (or later, depending on when it is believed that the soul enters the body) one of these pre-existent souls enters, or is placed by God, in the body. This belief is held to a varying degree in Abrahamic and other religions. Alternative positions are traducianism and creationism, which both hold that the individual human soul does not come into existence until conception.
The boundaries of the beforelife are debatable, since there is controversy over when a human life formally begins.
"The idea that certain things pre-exist in heaven has a long history in the Biblical and early Jewish traditions. Knowledge of this history is essential for an understanding of the idea of pre-existence in the New Testament" 
The earliest surviving Christian writings on the pre-existence were from Origen. Origen posited in a speculative work that the soul was assigned a body as a penalty for its sin of looking downward toward the corrupt earth. He also taught that Jesus Christ was actually born of the Father before the world began or before any other creatures existed.
"Jesus Christ Himself, who came, was born of the Father before all creatures; and after He had ministered to the Father in the creation of all things, for through Him all things were made."
The doctrine also derives in part from a repudiation of Greek thought by Tertullian, who argued that for each immaterial soul a material body was created.
The Old and New Testament address the question of pre-existence indirectly. For example, in Jeremiah 1:5 we read, "Before I [God] formed thee in the belly I knew thee." John 8:23 Jesus says: ‘You are from the realms below; I am from the realms above. You are from this world; I am not from this world.’” (Jesus did come from the spirit realm. But, as Jesus said, other men did not.) Romans 9:10-12 says: Re·bek′ah conceived twins ... when they had not yet been born nor had practiced anything good or vile, in order that the purpose of God respecting the choosing might continue dependent, not upon works, but upon the One who calls, it was said to her: “The older will be the slave of the younger.” (If the twins Jacob and Esau had lived previously in a spirit realm they certainly would have built up a record based on their conduct there. But they had no such record until after their birth as humans.) On the other hand, Paul says in Ephesians 1:4 that "he hath chosen us in him before the foundations of this world.
In historical Christian theology, Jesus pre-existed as the Word who created all things in heaven, or earth, visible and invisible, and also was born as the Son of God. (John 1:1-14; Colossians 1:15-16). While orthodox Christian doctrine insists that humanity did not pre-exist, there are those who postulate that the biblical tradition says otherwise.
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