First Vatican Council

The 1869–1870 ecumenical council of the Catholic Church defined papal primacy and papal infallibility under specified conditions in its constitution Pastor aeternus. The council was interrupted before completing its planned work.

Pastor aeternus: The First Vatican Council’s 1870 dogmatic constitution defining papal primacy and infallibility. This constitution contains the council’s defining statements on both doctrines.
Pius IX: Pope of the Catholic Church from 1846 to 1878, who convened the First Vatican Council. He called the council and guided its agenda amid challenges to papal authority.
Kingdom of Italy: The unified Italian state established in 1861, which incorporated Rome in 1870. Its capture of Rome ended the council’s sessions and papal temporal rule there.
Dei Filius: The First Vatican Council’s 1870 dogmatic constitution on Catholic faith and the relationship between faith and reason. It was the council’s other completed dogmatic constitution, preceding Pastor aeternus.
Papal infallibility: The Catholic doctrine that the pope is preserved from error when defining faith or morals for the whole Church under specified conditions. The council defined its conditions and limits in a solemn doctrinal formula.
Risorgimento: The nineteenth-century movement that unified the Italian states into the Kingdom of Italy. Italian unification threatened the Papal States during the council’s deliberations.
Roman Question: The dispute over the pope’s status and sovereignty after the Kingdom of Italy annexed Rome. The annexation that interrupted the council left papal sovereignty unresolved.
1870 capture of Rome: The Italian army’s occupation of Rome on 20 September 1870, ending papal rule over the city. The occupation forced the council to suspend its sessions indefinitely.
Papal primacy: The doctrine that the pope holds supreme authority and jurisdiction in the Catholic Church. The council affirmed the pope’s jurisdiction over the whole Church.
Papal States: Territories in central Italy ruled by the popes until their loss during Italian unification. Their impending loss formed the political crisis surrounding the council.

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