Blessed Pope Pius IX, born Giovanni Maria Mastai-Ferretti, reigned as Pope from 16 June 1846 to his death in 1878. He was the longest-reigning elected pope in the history of the Catholic Church – over 31 years. During his pontificate, he convened the First Vatican Council (1869–70), which decreed papal infallibility, but the council was cut short due to the loss of the Papal States.
Pius IX defined the dogma of the Immaculate Conception of the Blessed Virgin Mary, meaning that Mary was conceived without original sin. Pius IX also conferred the title Our Mother of Perpetual Help on a famous Byzantine icon from Crete entrusted to the Redemptorists.
He was also the last pope to rule as the Sovereign of the Papal States, which fell completely to the Italian army in 1870 and were incorporated into the Kingdom of Italy. After this, he was referred to – chiefly by himself – as the "Prisoner of the Vatican".
After his death in 1878, his canonization process was opened on 11 February 1907 by Pope Pius X and it drew considerable controversy over the years. It was closed on several occasions during the pontificates of Pope Benedict XV and Pope Pius XI. On 7 December 1954, Pope Pius XII re-opened the cause and Pope John Paul II proclaimed him Venerable on 6 July 1985. Together with Pope John XXIII he was beatified on 3 September 2000 after the recognition of a miracle and was assigned the liturgical feast day of February 7 which is the date of his death.
Excellent short treatise on the Immaculate Conception, plus the official definition of the dogma. All Catholics should read this. You can read it for free on the web at www.papalencylicals.net although the translation has a few minor word errors in it. Excellent.
Similar to my other review on Ven. Pope Pius XII work on the Assumption of Mary, its always good to supplement these works to get further background and insight on what is believed and why it is believed. I recommend ''On the Immaculate Conception'' by Dom Prosper Gueranger O.S.B. and again ''THE MOTHER OF THE SAVIOUR AND OUR INTERIOR LIFE'' by Fr. Garrigou-Lagrange O.P. which talks about it.
The document expresses a solid consideration of both exegetical, prophetic, theological, pious tradition, and authoritative letters for the universal proclamation of this belief that is held by Catholic Christians and as well as other apostolic churches but through other means.
this document helps solidify the dogmatization of the Immaculate Conception, pulls from many sources, but it did spend a lot of time reinforcing the authority of the Church and justifying the official celebration of the Conception (though perhaps this is due to extenuating circumstances). i personally felt that the following document, Munificentissimus Deus (1950) was more rounded in its explanations and delve deeper into theological discussion.