The law of original sin was relaxed only in one single case, for one soul that needed redemption. Upon the whole human race that was to be born, the curse was pronounced that no descendant of that first pair could escape the need of the Redeemer - however holy or sacred, however allied in kinship or work to the Incarnate God, however destined to precede or follow, to herald or remind the world of its Saviour. Each created human soul stood in need of a redeemer, required the Blood of Christ to be applied to itself before redemption could come to it. This none could avoid. The privileges of our Blessed Lady were many and great, but they could not include any such gift as that. God could not really allow her to be saved without the intervention of her Son. As much as I, so much did she, require the saving merits of her Son to be applied to her. Our Lord Himself alone out of all created nature needed no such justification. By His own power redemption had come: God as well as man, He stood in need of no redeeming. It was He, indeed, who was offended against, not He who had offended; but apart from Him, no other could escape. Even His mother must fall under the universal law. She, too, had to be ransomed, and any doctrine that implied her freedom from this requirement would be blasphemy against the word of God. This much must be borne in mind, then, before we can hope to understand the meaning of this privilege: unique as it was, it did not exempt our Lady from the need of redemption.
The difference, then, between her case and mine was not that I had to be redeemed and she had not, but only in the different ways in which that redemption was applied. We were both of us, our Lady and myself, redeemed - both cleansed from original sin. But with her it was, so to say, a preventative cleansing, with me a cleansing after the stain had already been made on the soul. Original sin, we must remember, is transmitted by means of the body. The soul comes to us straight from the hands of God. It is the only thing that is directly created by God. Everything else comes into the world through the mediation of secondary causes. The soul, since it is from God, could not arrive already laden with sin. There remains, therefore, the body, which is produced by means of the joint action of my parents. All flesh and blood (formed from them and thus descending ultimately from the single pair whence came the human race) brings with it the taint of sin. Not, of course, that the material could be sinful, but that it brings sin in its train. Nor, again, are we to imagine that at any moment th body exists without the soul: according to the ordinary scientific opinion of our time, the foetus from the first moment of existence contains human life. But though soul and body come together in an immediate embrace, it is still correct to say that it is from the body and not from the soul that the stain of sin comes, - for this reason, that the soul is of God, and the body of man.
By the privilege, then, of the Immaculate Conception we mean no more than that our Lady was redeemed by her Son and that the application of His merits to her soul was made in a way different from the way in which they were applied to others. She had a privilege, a special exception to a general law. Through no merits of her own, long before she was able to merit or demerit, solely through the action of her Son, she was preserved from all contagion of sin. She was already redeemed before she was conceived in the womb. Without in any way interfering with the work of His divine atonement, at the very moment of her conception the power of God warded from her the least stain of sin. In virtue of His sacred Passion, as yet only foreseen, her baptism was wrought without any ceremony and at the instant that her body and soul were united in an eternal embrace. Thus it is seen that so far from her privilege detracting in any way from the power of God, or her sinlessness being in any sense due to herself, God went out of His way to deal with her. She is, as always, the highest example that we know of the supreme mercy of God. Sometimes, perhaps, we are led to think of her as though she were in some way less beholden to Him than we are. Really she has received much more at His hands and owes Him love and gratitude that are far greater than ours. By the very splendour of grace with which He endowed her from the first instant of life, and by the never-failing spring of grace that grew greater from day to day, she has become the greatest miracle of all creation, the one part of creation that more than any other owes to Him debts beyond the possibility of humanity to repay. Salute her, then, my soul, because of her excellence, but salute God more for the existence of such perfection shown to our eyes, and for the wonderful thing that He has done for that human nature which she bears in common possession with us.
- text taken from Meditations for Layfolk by Father Bede Jarrett, O.P.