On 18 July 1870, Pastor Aeternus or the Dogmatic Constitution of the Church of Christ was approved by the First Vatican Council.
Pastor Aeternus was intended to emphasize the power and authority of the papacy in the face of political, social, and religious threats present in Europe and the world at the time. To emphasize that the Papacy could be relied upon as the source of truth in an environment in which the very notion of absolute truth that could be known was being called into question.
Thus, Pastor Aeternus, stresses that the primacy of the Pope comes from divine authority of and was instituted by Jesus Christ and that the authority of the Pope presides over the entire Church. One of the most important aspects of Papal authority is exercised in the Pope’s teaching authority, the
We teach and define that it is a dogma Divinely revealed that the Roman pontiff when he speaks ex cathedra, that is when in discharge of the office of pastor and doctor of all Christians, by virtue of his supreme Apostolic authority, he defines a doctrine regarding faith or morals to be held by the universal Church, by the Divine assistance promised to him in Blessed Peter, is possessed of that infallibility with which the Divine Redeemer willed that his Church should be endowed in defining doctrine regarding faith or morals, and that therefore such definitions of the Roman pontiff are of themselves and not from the consent of the Church irreformable.
So then, should anyone, which God forbid, have the temerity to reject this definition of ours: let him be anathema.
This declaration of Papal Infallibility was indeed controversial, even among the bishops present at the First Vatican Council. Many bishops who accepted Papal Infallibility still believed that the tense situation and likely negative response by secular society suggested that it would be imprudent to issue Pastor Aeternus at this time. This was a particular concern of the Bishops of the United States, France, and Germany. Indeed 60 bishops abstained from the vote on Pastor Aeternus by leaving Rome for their home countries on the day the vote was taken.
However, the large majority of bishops supported Pastor Aeternus and all of those who abstained did voice their acceptance of the document after it was confirmed at the First Vatican Council.
Negative reaction amongst some Catholics in Switzerland, Austria and Germany will lead to the formation of the Old Catholic Church. German Chancellor Otto von Bismark will begin his policy of persecution directed against the Catholic Church, the Kulturkampf, in response to Pastor Aeternus, arguing that German Catholic obedience to the papacy meant that they were not fully loyal to the German Kaiser.