The Immaculate Conception was solemnly defined as a dogma by Pope Pius IX in his constitution ''Ineffabilis Deus'', published [[December 8]], 1854 (the Latins' Feast of the Immaculate Conception). From 1483, Pope Sixtus IV had left Roman Catholics free to believe that Mary was subject to original sin or not, after having introduced the celebration; this freedom had been reiterated by the [[Wikipedia:Council of Trent|Council of Trent]].
The Roman Catholic Church believes the dogma is supported by scripture and by the writings of many of the [[Church Fathers]], either directly or indirectly. Roman Catholic theology maintains that since Jesus became [[incarnation|incarnate]] of the Virgin Mary, she needed to be completely free of sin to bear the Son of God, and that Mary is "redeemed 'by the grace of [[Christ]]' but in a more perfect manner than other human beings" (Ott, ''Fund.'', Bk 3, Pt. 3, Ch. 2, §3.1.e).
The doctrine is generally not shared by either Eastern Orthodoxy or by [[Protestantism]]. Protestantism rejects the doctrine because it is not explicitly spelled out in the [[Bible]]. Protestants and Eastern Orthodox often say that the immaculate conception of the [[Theotokos]] would contradict the doctrine of the [[salvation|redemption]] of humanity, as the Virgin Mary would have been cleansed before Christ's own incarnation, making his function superfluous. Orthodox Christians say that St. [[Augustine of Hippo|Augustine]] (d. 430), whose works were not well known in Eastern Christianity until perhaps the [[17th century|17th]] and [[18th century|18th]] centuries, has influenced the theology of sin that has generally taken root in the West. Many Orthodox consider unnecessary the doctrine that Mary would require purification prior to the Incarnation. Eastern Orthodox theologians believe that the references among the Greek and Syrian Fathers to Mary's purity and sinlessness may refer not to an ''a priori'' state but to her conduct after birth.