I’m not a theologian, so if someone more knowledgeable comes along then I’ll quickly defer. I don’t want you sitting there without any explanation, so I’ll try my best.
Mary restores humanity to the relationship we had with God in the Garden of Eden. What Eve undid, Mary set aright. Eve sinned, Mary obeyed. Eve separated us from God, Mary brought us reconciliation. Mary is the model of what we are all called to. The rest of us are kept from experiencing God fully and intimately because of our sins and the corruption that we’ve brought to our world, separating ourselves from Him. Mary is our model. Her obedience our example. Her complete unity with God our vision and knowledge of what awaits us.
She is without sin because we all should be. God shielded her from the effects of sin by His indwelling presence, as He would for each of us if we aligned our will entirely with His. Why her? Why not her mother or Elizabeth whose son was sanctified in the womb? Why Elijah? Why Moses? Why me? Because it was God’s will and He knows the entire creation story and knew exactly when and where and who would bring about His plan, just as he knows you and has a plan for you. And like Mary, we are called to carrying God in us in trust and obedience. Mary’s dormition and assumption provide a foretaste of what is to come now that our relationship with the Lord is restored. I hope someone who studies this will come along and better explain.
“He [Christ] became man by the Virgin, in order that the disobedience which proceeded from the serpent might receive its destruction in the same manner in which it derived its origin. For Eve, who was a virgin and undefiled, having conceived the word of the serpent, brought forth disobedience and death. But the Virgin Mary received faith and joy, when the angel Gabriel announced the good tidings to her that the Spirit of the Lord would come upon her, and the power of the Highest would overshadow her: wherefore also the Holy Thing begotten of her is the Son of God; and she replied, ‘Be it unto me according to thy word.’ And by her has He been born, to whom we have proved so many Scriptures refer, and by whom God destroys both the serpent and those angels and men who are like him; but works deliverance from death to those who repent of their wickedness and believe upon Him.” - St. Justin Martyr, Dialogue with Trypho, 100 (AD 150)
“And thus also it was that the knot of Eve’s disobedience was loosed by the obedience of Mary. For what the virgin Eve had bound fast through unbelief, this did the virgin Mary set free through faith.” - St. Irenaeus of Lyons, Against Heresies, 3, 22, 4 (AD 180)
“For it was while Eve was yet a virgin, that the ensnaring word had crept into her ear which was to build the edifice of death. Into a virgin’s soul, in like manner, must be introduced that Word of God which was to raise the fabric of life; so that what had been reduced to ruin by this sex, might by the selfsame sex be recovered to salvation. As Eve had believed the serpent, so Mary believed the angel. The delinquency which the one occasioned by believing, the other by believing effaced.” - Tertullian, On the Flesh of Christ, 17 (AD 200)
“… Christ found in the Virgin that which He willed to make His own, that which the Lord of all might take to Himself. Further, our flesh was cast out of Paradise by a man and woman and was joined to God through a Virgin.” - St. Ambrose of Milan, Letter to the Church at Vercellae, 33 (AD 396)
“Death came through Eve, but life has come through Mary.” - St. Jerome of Stridonium, Letter to Eustochium, 21 (AD 384)
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