Leo XIII – Octobri mense (1891): Mary, Co-Redemptrix and Mediatrix of All Graces (Doctrina Pontificia IV, nn. 372-388)

The encyclical Octobri mense (September 22, 1891) of Leo XIII is, by the consensus of Mariologists, the most important and theologically rich of his thirteen encyclicals on the Rosary. The document develops the doctrine of Mary’s cooperation in the redemption — the so-called “co-redemption” — with a precision and depth without precedent in the pontifical Magisterium. Numbers 372-388 of Doctrina Pontificia IV cover this encyclical.

The doctrine of co-redemption

Octobri mense contains Leo XIII’s boldest formulation on Mary’s role in salvation. The pope develops the Eve/Mary parallel inaugurated by Saint Irenaeus: as Eve cooperated with Adam in the fall of the human race, Mary cooperated with Christ in the redemption of the human race.

«Quod [Deus] Filium suum unigenitum dare decrevit… eam [Mariam] quasi Matrem elegit; et propter hanc tam praeclaram dignitatem voluit ut omnium beneficiorum, quae nec in terra nec in caelo obtineri a nobis possunt nisi per Iesum Christum Mediatorem nostrum, per Mariam quoque intercedente Maria haberentur»

, What God decided to give in His only-begotten Son… He chose her [Mary] as Mother; and because of so illustrious a dignity, He willed that all the benefits that, neither on earth nor in heaven, can be obtained by us except through Jesus Christ our Mediator, should also be had through the intercession of Mary.

“Nihil nos Deus habere voluit quod per mariam non transiret”

The most quoted phrase of the encyclical — “God willed that nothing should come to us without passing through Mary” — sums up in a single line the Leonine doctrine of Marian mediation. This phrase, attributed by Leo XIII to Saint Bernard, became one of the classic axioms of the mariology of mediation, taken up by Pius X, Pius XII, and Blessed Paul VI.

Mary as the New Eve in the Rosary

Leo XIII presents the Rosary as the contemplative itinerary of the New Eve: from the Joyful Mysteries (Mary’s cooperation in the Incarnation) to the Sorrowful (Mary’s cooperation in the Passion, at the foot of the Cross) to the Glorious (the glorification of Mary crowned in Heaven). To pray the Rosary is to contemplate Mary’s cooperation in the history of salvation.

Significance for contemporary Mariology

Octobri mense of 1891 anticipates the dogmatic definitions of the twentieth century:

• The Assumption defined by Pius XII in 1950 (Munificentissimus Deus): Leo XIII already affirms that Mary is glorified in Heaven
• The Queenship defined by Pius XII in 1954 (Ad Caeli Reginam): Leo XIII already uses the title of “Queen” in the context of the Rosary
• Lumen Gentium VIII of the Second Vatican Council: the doctrine of Mary’s cooperation that Leo XIII elaborates is taken up systematically by the Council

Further reading

Explore Mariology, Rosarium Virginis Mariae (John Paul II, 2002), Munificentissimus Deus, Ad Caeli Reginam, and the Postgraduate Program in Mariology.