The Preface prayer from the Mass for this holy day gives us a short lesson in the theology of the Immaculate Conception:
Father, all-powerful and ever-living God,
we do well always and everywhere to give you thanks.
You allowed no stain of Adam’s sinto touch the Virgin Mary.
Full of grace,
she was to be a worthy mother of your Son,
your sign of favor to the Church at its beginning,
and the promise of its perfection
as the bride of Christ,radiant in beauty.
Purest of virgins, she was to bring forth your Son,
the innocent lamb who takes away our sins.
You chose her from all women
to be our advocate with you
and our pattern of holiness.
In our joy we sing to your glory
with all the choirs of angels:
Holy, holy, holy ...