Assumption

Defined as "The taking into Heaven of the soul and body of the Blessed Virgin on the completion of her earthly life, by an anticipation of the general judgment. (Definition from A Catholic Dictionary, 1951)

Church Teaching:

"Nothing is handed down in the canonical Scriptures concerning the sanctification of the Blessed Mary as to her being sanctified in the womb; indeed, they do not even mention her birth. But as Augustine, in his tractate on the Assumption of the Virgin, argues with reason, since her body was assumed into heaven, and yet Scripture does not relate this; so it may be reasonably argued that she was sanctified in the womb. For it is reasonable to believe that she, who brought forth "the Only-Begotten of the Father full of grace and truth," received greater privileges of grace than all others: hence we read (Lk. 1:28) that the angel addressed her in the words: "Hail full of grace!" St. Thomas Aquinas, Summa Theologica (13th century), Whether the Blessed Virgin was sanctified before her birth from the womb?

"According to the life of St. Theodosius (d. 529) it (Feast of the Assumption) was celebrated in Palestine before the year 500, probably in August (Baeumer, Brevier, 185). In Egypt and Arabia, however, it was kept in January, and since the monks of Gaul adopted many usages from the Egyptian monks (Baeumer, Brevier, 163), we find this feast in Gaul in the sixth century, in January [mediante mense undecimo (Greg. Turon., De gloria mart., I, ix)]. The Gallican Liturgy has it on the 18th of January, under the title: Depositio, Assumptio, or Festivitas S. Mariae (cf. the notes of Mabillon on the Gallican Liturgy, P. L., LXXII, 180). This custom was kept up in the Gallican Church to the time of the introduction of the Roman rite. In the Greek Church, it seems, some kept this feast in January, with the monks of Egypt; others in August, with those of Palestine; wherefore the Emperor Maurice (d. 602), i"f the account of the "Liber Pontificalis" (II, 508) be correct, set the feast for the Greek Empire on 15 August." 1917 Catholic Encyclopedia, The Feast of the Assumption

"....that whenever they preach to the people on the first, fourth and last Sundays of Lent, and on the feasts of the Ascension of the Lord, Pentecost, the Birthday of blessed John the Baptist, the Assumption and the Birthday of the most blessed virgin Mary, the mother of God...." Council of Vienne, 1311-1312

"Thus, from the universal agreement of the Church's ordinary teaching authority we have a certain and firm proof, demonstrating that the Blessed Virgin Mary's bodily Assumption into heaven- which surely no faculty of the human mind could know by its own natural powers, as far as the heavenly glorification of the virginal body of the loving Mother of God is concerned-is a truth that has been revealed by God and consequently something that must be firmly and faithfully believed by all children of the Church. For, as the Vatican Council asserts, "all those things are to be believed by divine and Catholic faith which are contained in the written Word of God or in Tradition, and which are proposed by the Church, either in solemn judgment or in its ordinary and universal teaching office, as divinely revealed truths which must be believed." Encyclical On Defining the Dogma of the Assumption by Pope Pius XII issued November 1, 1950

"And, although the Church has always recognized this supreme generosity and the perfect harmony of graces and has daily studied them more and more throughout the course of the centuries, still it is in our own age that the privilege of the bodily Assumption into heaven of Mary, the Virgin Mother of God, has certainly shone forth more clearly." Encyclical On Defining the Dogma of the Assumption by Pope Pius XII issued November 1, 1950

"Today, the belief in the corporeal assumption of Mary is universal in the East and in the West; according to Benedict XIV (De Festis B.V.M., I, viii, 18) it is a probable opinion, which to deny were impious and blasphemous." 1917 Catholic Encyclopedia, The Feast of the Assumption, The Fact of the Assumption

Summary

The Assumption of the Blessed Virgin Mary has been believed universally throughout the history of the Catholic Church. So universal and long standing has this teaching been in the Catholic Church, that it was defined a Catholic Dogma in 1950 through the solemn magisterium of the Church. Those who do not believe in this dogma cannot call themselves Catholic!