What doctrine regarding the Pope was formally defined at the First Vatican Council?

The doctrine of papal infallibility was formally defined at the First Vatican Council, which took place from 1869 to 1870. This doctrine asserts that the Pope, under certain conditions, is preserved from error when proclaiming dogmas related to faith and morals. The council articulated that this infallibility is not a personal attribute of the Pope himself but a protection granted by the Holy Spirit when he speaks ex cathedra, or from the chair of St. Peter, concerning matters of doctrine.

The establishment of this doctrine was significant in affirming the Pope’s authority within the Catholic Church. It reinforced the belief that the Pope, as the successor of St. Peter, holds a unique position that allows him to resolve theological disputes and provide definitive teachings that all Catholics are expected to adhere to.

Other doctrines mentioned, such as papal supremacy, while significant, were not formally defined at this specific council. Papal supremacy relates to the Pope's overall authority over the Church but was already widely acknowledged prior to the First Vatican Council. Doctrines like original sin and transubstantiation pertain to different theological concepts that were not the focus of the First Vatican Council's declarations. Thus, the emphasis on papal infallibility stands out