Pius IX defines the Immaculate Conception; CCWV.LIFE

On 8 December 1854, in the bull Ineffabilis Deus, Pius IX defines as dogma that Mary, at the first instant of her conception, was preserved exempt from all stain of original sin. It is the first dogma a pope defines on his own authority in the modern form, a generation before Vatican I defines the infallibility such an act presupposes.

Tagged: Catholic

The Event

Date: 1854 (exact)
Era: Revolution and the Nineteenth Century; Standard periodization of Catholic history
Location: Rome; today Rome, Italy
Traditions: Catholicism
Streams: Catholic
Key figures: Pius IX
Key texts: Ineffabilis Deus

How the Tradition Tells It

The definition is received by the Catholic church as dogma; the Eastern Orthodox and Protestant churches do not accept it, and the record states the act without adjudicating it.

Connections

History Event First Vatican Council 1869–1870 prefigures the infallibility the council defines sixteen years later

Primary Sources

Pius IX, Ineffabilis Deus, 1854.

Secondary Sources

Chadwick, Owen. A History of the Popes, 1830-1914. Oxford: Clarendon Press, 1998.
Duffy, Eamon. Saints and Sinners: A History of the Popes. New Haven: Yale University Press, 2006.
Hastings, Adrian, ed. A World History of Christianity. Grand Rapids: Eerdmans, 1999.
MacCulloch, Diarmaid. A History of Christianity: The First Three Thousand Years. London: Penguin, 2009.
O'Malley, John W. Trent: What Happened at the Council. Cambridge, MA: Harvard University Press, 2013.

Provenance: HIST-1338; confidence 0.95; accessed 2026-10-30.