On December 8, 1854, Pope Pius IX (1846-78) defined that “the most blessed Virgin Mary…was preserved free from all stain of original sin..”. This definition did not come as a surprise but was the culmination of long years of preperation. It is interesting to note this historical development :

1) Pope Sixtus IV (1471-84) gives approval to the feast

2) Pope Innocent VIII (1484-92) gives approval to the invocation of Mary under the title of the Immaculate Conception

3) At the Council of Trent (1545-63) the fathers did not want the decree on original sin to be understood as including the blessed Virgin

4) In 1567, Pope St. Pius V (1566-72) condemned the proposition of Michael de Bay; during his pontificate the Office of the Immaculate Conception was introduced into the breviary

5) Pope Paul V (1605-21) forbade anything contrary to the teaching of Mary’s Immaculate conception to be said in public

6) In 1622, Pope Gregory XV (1621-23) forbade any contrary statements to be made in private

7) Pope Alexander VII (1655-67) declared that the object of the devotion is the conception of the Blessed Virgin Mary. It is interesting to note that Pope Alexander’s statement was incorporated almost verbatim into Pope Pius IX’s definition of the dogma

8) Pope Clement XI (1700-21) made the feast one of the precept in the universal church

(The Church Teaches: Documents of the Church in English Translation, Jesuit Fathers of St. Mary’s College , page 207-8)