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Pope Pius IX issued the apostolic constitution *Ineffabilis Deus* to formally de
Featured Event 1854 Event

December 8

Immaculate Conception Defined: Pope Declares Mary's Dogma

Pope Pius IX issued the apostolic constitution *Ineffabilis Deus* to formally declare that the Virgin Mary remained free from original sin from the moment of her conception. This definitive ruling settled centuries of theological debate by establishing a core Catholic dogma that shaped Marian devotion and church authority for generations.

December 8, 1854

172 years ago

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