A corruptible Life -
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The Life that the elect had in Adam in the beginning was a corruptible life, capable of and indeed became corruption. ; But that life God had prepared for His chosen people for eternity was incorruptible per 1 pet 1:
4To an inheritance incorruptible, and undefiled, and that fadeth not away, reserved in heaven for you,
This life had to come through the Last Adam, and they [ elect] had to be born of His incorruptible seed instead of Adam's corruptible seed 1 pet 1:
23Being born again, not of corruptible seed, but of incorruptible, by the word of God, which liveth and abideth for ever.
Adam's seed was corruptible as was evidenced in the garden gen 3, Christ seed was incorruptible as evidenced in the Christ temptation lk 4.
The elect had been chosen in Christ [ The Last Adam] before they had been created in the First Adam, because the Last Adam, though not manifested first [ 1 jn 3:5,8] He did exist first, and He existed as the head of His body, the church col 1:
16For by him were all things created, that are in heaven, and that are in earth, visible and invisible, whether they be thrones, or dominions, or principalities, or powers: all things were created by him, and for him:
17And he is before all things, and by him all things consist.
18And he is the head of the body, the church: who is the beginning, the firstborn from the dead; that in all things he might have the preeminence.
The elect by the wisdom of God, had incorruptible life given them first in Christ their preexisting head, before they were given corruptible life in their earthly head Adam.