Immaculate Conception
Post-Apostolic:
Implicitly found in the Fathers of the Church in the parallelism between Eve and Mary (Irenaeus, Lyons, 140? - 202?); Found in the more general terms about Mary: “holy”, “innocent”, “most pure”, “intact”, “immaculate” (Irenaeus, Lyons, 140?-202?; Ephraem, Syria, 306-373; Ambrose, Milan, 373-397); Explicit language: Mary - free from original sin (Augustine, Hippo, 395-430 to Anselm, Normandy, 1033-1109).
Celebrations:
[Eastern Church] celebrated a “Feast of the Conception of Mary” in the 8th to the 9th Century; Western Church: celebrated a Feast of the Conception of Mary in the 12th Century; A record of the feast in the 11th Century in Great Britain; in the 12th Century in Normandy; Record in many churches of a Feast of the Conception of Mary in France, Germany, Italy and Spain in the 12th Century (Bernard, Clairvaux, 1090-1153).
14th Century:
Was noted for the opposition to the Immaculate Conception from some of the great doctors of scholasticism. The celebration of the feast was not denied though. The difficulty arose from the meaning of the universal redemption through Christ.
15th Century:
Franciscan theologians solved the difficulty. Christ, the most perfect mediator, preserved Mary from original sin by an equally perfect act of healing. Duns Scotus (Scotland, 1266-1308) explained that the Immaculate Conception came through God’s application of the grace of Christ beforehand.
From 15th Century:
The Feast was universally celebrated; and christian piety introduced an oath to defend the belief in the Immaculate Conception to be taken not only by Religious, but also by non-Religious and at the Universities (e.g., Paris, 1497; Cologne, 1499; Vienna, 1501)
From the 17th Century:
The clause “to the shedding of blood” was added to the oath taken to defend the belief in the Immaculate Conception.
1854
Pope Pius IX, infallibly defined, ex cathedra: “The Blessed Virgin Mary, in the first instant of her conception, by a singular grace and privilege of Almighty God, and in view of the foreseen merits of Jesus Christ, the savior of the human race, was preserved free from all stain of original sin.”
Nonbelievers and enemies of Roman Catholic Christianity often accuse the Church of creating the belief in Mary’s freedom from original sin “the Immaculate Conception” in 1854 (as the Church named the belief of Mary’s immediate entry, body and soul, into Heaven, “the Assumption” in 1950) when the truths were defined. Such an error is equivalent to saying that before Adam named the animals and birds of creation in Gen 2:19-20 they did not exist. Or that before the early Church in her Ecumenical Councils named the belief of three persons in one God “the Trinity” and the belief that there are two natures, human and divine in the person of Jesus Christ “the Incarnation,” the truths did not exist.
Amazing how the EO overlooks its own history as well as Angelican posting here.