In the 11th century a Benedictine monk Eadmerus, a disciple of Anselm, wrote a Tractatus de concepitone sanctae Mariae decisively in favour of the popular belief, in which he says he agrees that Mary was conceived without stain of sin.
In 1435, at the Council of Basle, John Ramiroy appealed to popular devotion as the main reason to induce the Council Fathers to come to a conclusion with regard to the Immaculate Conception of Mary in order not to scandalise the Christian people offended by the those who affirmed that Mary was defiled by original sin.
During its 36th session (17 September 1439) the Council issued a decree declaring that belief in the immaculate Conception was authentic, in keeping with the liturgy of the Church, the Catholic faith, Sacred Scripture and common sense, and so it could be held by all Catholics and no one was to teach the contrary.
Examining the magisterial interventions on the theme of the Immaculate Conception we can say that no Pope ever expressed the ‘maculista’ opinion in his teaching.
Although Pope Sixtus IV, in the 15th century took no decision on the question, he did issue two Papal Bulls, Cum praexcelsa in 1477 and Grave nimis in 1483, banning those for and against from launching reciprocal accusations. He also adopted liturgically for Rome the feast of the Immaculate Conception, approving a new formula composed by Leonardo di Nogarole and Bernardino di Busto, expressing the Marian privilege.
During the years, biblical and patristic research gathered new facts to the point that during the 6th session of the Council of Trent (1546) there were some who called for the definition of the dogma of the Immaculate Conception. However because the Council had been called to counter heretic theories of the day the idea was abandoned in favour of an appendix to the decree on the universality of original sin, which was the following: “This Holy Synod declares its intention not to include in the decree on original sin, the Blessed and Immaculate Virgin Mary, Mother of God, while affirming that the Constitutions issued by Pope Sixtus IV must be observed.”
In the 17th century there were interventions by three other Popes: Paul V, shocked by disputes between those in favour and against, prohibited anyone from expressing in public dissent with regard to teaching in favour of the Immaculate Conception; Gregory XV forbade all manifestations of dissent, even in private. Alexander VII promulgated the Constitution Sollicitudo omnium Ecclesiarum explaining the precise object of the feast which concerned the preservation of Mary’s soul from original sin from the first moment of its conception when it was infused in her body, through special grace and privilege granted by God in view of the merits of Christ, the redeemer of mankind.
The constitution had exceptional repercussions and its most fruitful expression was the institution of various fraternities named after the Immaculate Conception.
In the same period in some European universities a movement started in favour of the Immaculate Conception which proposed a votum sanguinis to defend the Immaculate Conception of Mary even to death. The initiative was harshly criticised by Ludovico Antonio Muratori who said it was imprudent, born of an ingenuous faith and lacked theological support.
Nevertheless certain factors helped to strengthen the sensus fidelium including preaching by Franciscans, connected since 1621 with an oath in favour of the Immaculate Conception, the Bellarmino catechism and in 1708, an act by Clement XI to extend to the universal Church the liturgical feast of the Immaculate Conception celebrated since the 9th century in southern Italy thanks to influence from the East.