Ineffabilis Deus in the context of "Munificentissimus Deus"

The Immaculate Conception is the doctrine that the Virgin Mary was free of original sin from the moment of her conception. It is one of the four Marian dogmas of the Catholic Church. Debated by medieval theologians, it was not defined as a dogma until 1854, by Pope Pius IX in the papal bull Ineffabilis Deus. While the Immaculate Conception asserts Mary's freedom from original sin, the Council of Trent, held between 1545 and 1563, had previously non-dogmatically affirmed her freedom from personal sin.

The Immaculate Conception became a popular subject in literature, but its abstract nature meant it was late in appearing as a subject in works of art. The iconography of Our Lady of the Immaculate Conception shows Mary standing, with arms outstretched or hands clasped in prayer. The feast day of the Immaculate Conception is December 8.

Scotism is the philosophical school and theological system named after John Duns Scotus, a 13th-century Scottish philosopher-theologian. The word comes from the name of its originator, whose Opus Oxoniense was one of the most important documents in medieval philosophy and Roman Catholic theology, defining what would later be declared the dogma of the Immaculate Conception by Pope Pius IX in his constitution Ineffabilis Deus on 8 December 1854.