The Immaculate Conception is, according to Roman Catholic dogma, the conception of Mary, the mother of Jesus without any stain of original sin, in her mother's womb: the dogma thus says that, from the first moment of her existence, she was preserved by God from the lack of sanctifying grace that afflicts mankind, and that she was instead filled with divine grace. It is further believed that she lived a life completely free from sin. Her immaculate conception in the womb of her mother, by normal sexual intercourse (Christian tradition identifies her parents as Sts. Joachim and Anne), should not be confused with the doctrine of the virginal conception of her son Jesus. The feast of the Immaculate Conception, celebrated on December 8, was established as a universal feast in 1476 by Pope Sixtus IV. He did not define the doctrine as a dogma, thus leaving Roman Catholics freedom to believe in it or not without being accused of heresy; this freedom was reiterated by the Council of Trent. The existence of the feast was a strong indication of the Church's belief in the Immaculate Conception, even before its 19th century definition as a dogma. In the Roman Catholic Church, the Solemnity of the Immaculate Conception is a Holy Day of Obligation, except where conferences of bishops have decided, with the approval of the Holy See, not to maintain it as such. It is a public holiday in some countries where Roman Catholicism is predominant e.g. Italy. In the Philippines, although this is not a public holiday, the predominance of Catholic Schools make it almost a holiday. The Immaculate Conception was solemnly defined as a dogma by Pope Pius IX in his constitution Ineffabilis Deus, on December 8, 1854. The Roman Catholic Church believes the dogma is supported by Scripture (e.g. Mary's being greeted by Angel Gabriel as "full of grace" or "highly favoured"), as well as either directly or indirectly by the writings of many of the Church Fathers, and often calls Mary the Blessed Virgin (Luke 1:48). Catholic theology maintains that, since Jesus became incarnate of the Virgin Mary, it was fitting that she be completely free of sin for expressing her fiat. (Ott, Fund., Bk 3, Pt. 3, Ch. 2, 3.1.e).