When Mary of Nazareth conceived in Her womb the Word of God, that conception was the effect of the fullness of Her grace, and of an action of the Holy Spirit which occurred in Her soul first of all, thereby making of Her flesh a tabernacle and a sanctuary. The dignity of the Mother of God is Her great sanctity, it is the incomparable grace which raises Her above all the Angels, the grace in which She was predestined and created for this glorious purpose. By the acts of Her blessed Maternity, She bordered on divinity while remaining entirely human. In this way She seems to exhaust, as it were, the power of God — the fullness of the grace accorded Her cannot be surpassed. It is easier for us to conceive of the greatness of Mary, however, when we consider Her maternity of the Mystical Body, the Church, which like Herself is entirely human, and composed of persons who are very far indeed from being what our Saviour was, a Divine Person incarnate.
We understand better what Mary is for the Church by listening to Saint Louis Mary de Montfort, Apostle of the Cross and of the Rosary of Our Lady. As Mary was necessary for God in the Incarnation of the Word, so She is necessary for Him to sanctify souls and bring about their likeness to Christ, and She is much needed by us, in our great infirmity:
The Holy Ghost gives no heavenly gift to men which He does not have pass through Her virginal hands…; such is the sentiment of the Church and its holy Fathers. Mary, being altogether transformed into God by grace and by the glory which transforms all the Saints into Him, asks nothing, wishes nothing, does nothing contrary to the eternal and immutable Will of God. When we read then in the writings of Saints Bernard, Bernardine, Bonaventure and others, that in heaven and on earth everything, even God Himself, is subject to the Blessed Virgin, they mean that the authority which God has been well pleased to give Her is so great that it seems as if She had the same power as God; and that Her prayers and petitions are so powerful with God that they always pass for commandments with His Majesty, who never resists the prayer of His dear Mother, because She is always humble and conformed to His Will. If Moses, by the force of his prayer, stayed the anger of God against the Israelites in a manner so powerful that the most high and infinitely merciful Lord, being unable to resist him, told him to let Him alone that He might be angry with and punish that rebellious people, what must we not, with much greater reason, think of the prayer of the humble Mary, the worthy Mother of God, which is more powerful with His Majesty than the prayers and intercessions of all the Angels and Saints both in heaven and on earth?
The sin of our first father has spoiled us all, soured us, puffed us up and corrupted us… The actual sins which we have committed, whether mortal or venial, pardoned though they may be, have nevertheless increased our concupiscence, our weakness, our inconstancy and our corruption, and have left evil remains in our souls… We have nothing for our portion but pride and blindness of spirit, hardness of heart, weakness and inconstancy of soul, revolted passions, and sicknesses in the body… Let us say boldly with Saint Bernard that we have need of a mediator with the Mediator Himself, and that it is the divine Mary who is most capable of filling that charitable office. It was through Her that Jesus Christ came to us, and it is through Her that we must go to Him. If we fear to go directly to Jesus Christ, our God, whether because of His infinite greatness or because of our vileness, or because of our sins, let us boldly implore the aid and intercession of Mary, our Mother. She is good, She is tender, She has nothing in Her that is austere and forbidding, nothing too sublime and too brilliant… She is so charitable that She repels none of those who ask Her intercession, no matter how great sinners they have been; for, as the Saints say, never has it been heard, since the world was the world, that anyone has confidently and perseveringly had recourse to our Blessed Lady and yet been repelled. (True Devotion to Mary)
True Devotion to Mary, by Saint Louis Mary de Montfort(Montfort Publications: Bay Shore, 1960); Les Petits Bollandistes: Vies des Saints, by Msgr. Paul Guérin (Bloud et Barral: Paris, 1882), Vol. 12