The doctrine of the Holy Eucharist consist of that of the Eucharist sacrifice, the sacrificial meal, and the sacrificial food, or to express it otherwise, it consists of the doctrine of the Mass, of Communion, and of the Real Presence. There is no presence of Christ in the Blessed Sacrament that is not meant first and foremost as food for the faithful people, and there is no sacramental union with Christ in Holy Communion that is not to be thought of as a sacrificial meal: 'For as often as you shall eat this bread, and drink the chalice, you shall show the death of the Lord, until he come' (1 Cor. 11:26). The Eucharistic meal can only be prepared in the sacrifice of the Mass.
Thus the mystery of the Eucharist summarizes the whole mystery of our redemption. There are two fundamental relationships in which Christ stands to us. First, he is our priestly mediator with God, and offers him atonement for our sins. Bust Christ is not a stranger to us, who merely represents us as a propitiator before God. He comes to us in the second relationship by being the mediator of the grace which God gives us on account of his sacrifice. That is the mystery of our union with Christ who is the source of all grace for us. 'And of his fullness we have all received, grace for grace' (John 1:16).