The history of a dogma is of great importance in order to understand how the church arrives at the definition of a particular belief. In the case of the dogma of the Immaculate Conception, the historical development is especially significant because of lack of explicit scriptural evidence.
Already from the third century on there was a strong conviction that Mary was without sin. The Mother of Jesus Christ was compared to the incorruptible wood of the ark of the covenant and therefore without stain, immaculate, innocent and integral. In the East, Mary was considered the All Holy One (Panhagia).
The difficulty with celebrating Mary’s conception was the certainty that every person is conceived with original sin as Romans 5:12 states: "As through one man sin entered the world, and through sin death, so death passed to all men, in as much as all sinned."
Paschasius Radbertus (786 – 860), a pioneer in Marian Doctrine, approached the issue with the inquiry whether or not it was appropriate to celebrate the birthday of Mary? Usually, the church celebrates the death day of a saint commemorating his or her new life in heaven. By commemorating Mary’s birthday, the question arose again whether Mary was exempt from original sin.
Eadmer of Canterbury (1124) was the first theologian of the Immaculate Conception. He is famous for "Potuit, voluit, facit." He [God] could, he wanted, he did [create Mary free from original sin]!
We praise you, Mary, Virgin and mother. After the Savior himself, you alone are all holy, free from all stain of sin, gifted by God from the first instant of your conception with a unique holiness.