CONCEPTION, Immaculate, of the Holy Virgin, is a feast established in honour of the holy virgin, particularly with regard to her having been conceived and born immaculate, i. e. without original sin, held in the Romish church on the 8th of December. The immaculate conception is the great head of controversy between the Scotists and Thomists; the former maintaining, and the latter impugning it. In the three Spanish military orders, of St James of the sword, Calatrava, and Alcantara, the knights take a vow at their admission to defend the immaculate conception. This resolution was first taken in 1652. Peter d'Alva has published 48 huge volumes in folio on the mysteries of the conception.