Ineffabilis Deus (Latin for "Ineffable God") is the name of a Papal bull by Pope Pius IX. It defines ex cathedra the dogma of the Immaculate Conception of the Blessed Virgin Mary. The decree was promulgated on December 8, 1854, the date of the annual Feast of the Immaculate Conception. The dogmatic statement is expressed near the end of the document: The entire decree is also worded to suggest that Mary's Immaculate Conception was not in any sense a logical necessity, but rather a divine gift to Mary as Mother of God.