The Immaculate Conception is the Catholic doctrine that Mary was conceived without original sin, preserved from the first instant of her existence by a singular grace in view of the merits of Christ. The confusion the feast most often meets is with the virginal conception of Jesus: the Immaculate Conception concerns Mary's own conception by her parents, traditionally named Joachim and Anne, not the conception of her son. Its date, 8 December, sits nine months before the feast of Mary's nativity on 8 September.
The belief was long contested in the medieval West. Thomas Aquinas and others hesitated, holding that it seemed to exempt Mary from the universal need of redemption; the objection was met by the Scotist solution, associated with Duns Scotus, that Mary was redeemed more perfectly, by preservation rather than rescue. Pope Pius IX defined the doctrine as dogma in 1854 in the bull Ineffabilis Deus. The Eastern churches keep a related feast of the Conception of the Theotokos (9 December) without the specific Western definition. It is a holy day of obligation across much of the Catholic world and the patronal feast of several nations.