Britannica Sources used in this answer

How did Pope Pius IX use papal infallibility when declaring the Immaculate Conception?

Created from Britannica articles using AI. AI can make mistakes, so verify using Britannica articles.

The First Vatican Council — papal infallibility In 1869 Pope Pius XI (center) convened an assembly of bishops that became known as the First Vatican Council (or Vatican I). The council declared the dogmas of papal primacy and papal infallibility before the assembly was suspended indefinitely in 1870.

Pope Pius IX utilized the concept of papal authority, which would later be formally defined as papal infallibility, when he declared the dogma of the Immaculate Conception in 1854. While the doctrine of papal infallibility was officially defined in 1870 at the First Vatican Council, Pius IX acted under the belief that the pope, as the successor to St. Peter, could not err in matters of faith and morals.123456

The doctrine of the Immaculate Conception, proclaimed by Pius IX, asserts that the Virgin Mary was conceived without original sin due to God's grace. This declaration was a significant event during his pontificate, which was marked by a shift towards conservatism and a desire to centralize and strengthen the church's authority in response to secular ideas.2643