In Roman Catholicism , the dogma that Mary was not tainted by original sin .
Early exponents included St. Irenaeus ; St. Bonaventure and St. Thomas Aquinas were among those who opposed it. In 1439 the Council of {{link=Basel, Council of">Basel stated that the belief was in accordance with Catholic faith, and in 1709 Pope Clement XI made the feast of the Immaculate Conception a holy day of obligation. In 1854 Pius IX issued a papal bull making it official church dogma. See also Virgin Birth .