This Solemnity of the Church and Holy Day of Obligation calls our attention to an important doctrine. To define what the Immaculate Conception is helps Catholics to understand what they are called to believe as a faith tradition.
The Immaculate Conception means that Mary, whose conception was brought about the normal way, was conceived without original sin or its stain—that’s what “immaculate” means: without stain.
The essence of original sin consists in the deprivation of sanctifying grace, and its stain is a corrupt nature. Mary was preserved from these defects by God’s grace; from the first instant of her existence she was in the state of sanctifying grace and was free from the corrupt nature original sin brings.
This implicit reference may be found in the angel’s greeting to Mary. The angel Gabriel said, “Hail, full of grace, the Lord is with you” (Luke 1:28). The phrase “full of grace” is a translation of the Greek which expresses a characteristic quality of Mary.
This characteristic quality is much more than an identity of “highly favored daughter” found with some New Testament translations. The Greek implies the grace given to Mary is at once permanent and of a unique kind. There is a sense in its meaning “to fill or endow with grace.” This sense further indicates that Mary was graced in the past but with continuing effects in the present.
The grace Mary enjoyed was not a result of the angel’s visit. The state of sanctifying grace extended over the whole of her life, from her immaculate conception onward.
Because this feast day falls on Sunday this year, the Solemnity is transferred to Monday, December 9, but the Holyday of Obligation is not. (9:2)