A: This often misunderstood phrase refers to the conception of Mary through the marital union of her parents. At the very start of her life, Mary was free from the original sin which is universally 'inherited' by the descendents of Adam and Eve after the Fall. This unique privilege was granted through the merits of Christ in view of Mary's foreseen role as His Mother. Though the phrase could be applied to Jesus, who was also entirely free from original sin, the conventional language referring to His origins is "the Virgin Birth" or "the virginal conception." Unlike Mary, Jesus had no biological father (cf. Mt 1 and Lk 1).