The Assumption of Mary into heaven is the oldest of the Marian feasts, kept in the East since at least the fifth century and in the West since the seventh. The tradition holds that at the end of her earthly life Mary was taken up — body and soul, not separated by death and decay — into the glory of her Son. Pope Pius XII defined the doctrine formally in 1950, ending centuries of teaching it as a pious belief.
The theology is dense and luminous. Mary, the New Eve, who bore the Author of Life, is also the first to share in the bodily resurrection he won — a sign and a foretaste of what awaits all the faithful. The Eastern Churches keep the same mystery under the name Dormition, the falling-asleep, with prayer and a great fast in preparation.