A title of the Blessed Virgin as mediator of grace. There are two aspects of this mediation. It is certain in Catholic theology that, since Mary gave birth to the Redeemer, who is source of all grace, she is in this way the channel of all graces to mankind. But it is only probable, as a legitimate opinion, that since Mary's Assumption into heaven no grace is received by humans without her actual intercessory co-operation.
On the first level of mediation, Mary freely co-operated with God in consenting to the Incarnation, giving birth to her Son and thus sharing with him in spirit the labors of his passion and death. Yet Christ alone truly offered the sacrifice of atonement on the Cross. Mary gave him moral support in this action. She is therefore not entitled to the name "priest," as several Roman documents legislate. As explained by the Council of Florence in 1441, Christ "conquered the enemy of the human race alone" (Denzinger, 1347). In the same way he alone acquired the grace of redemption for the whole human race, including Mary. Her part in the objective redemption, therefore, was indirect and remote, and derived from her voluntary devotion to the service of Christ. Under the Cross she suffered and sacrificed with him, but subordinate to him in such a way that all the efficacy of her oblation depended on that of her Son.
On the second stage of mediation, Mary co-operates by her maternal intercession in applying Christ's redemptive grace to human beings, called the subjective redemption. This does not imply that the faithful must pray for all graces through Mary, nor that her intercession is inherently necessary for the distribution of divine blessing, but that, according to God's special ordinance, the graces merited by Christ are conferred through the actual intercessory mediation of his mother. Recent popes and the Second Vatican Council have spoken in favor of this type of mediation, which finds support in patristic tradition.