Pastor aeternus is the incipit of the Dogmatic Constitution on the Church of Christ, issued by the First Vatican Council, July 18, 1870. According to The Modern Catholic Dictionary, Pastor aeternus defines four doctrines of the Catholic faith: the apostolic primacy conferred on Peter, the perpetuity of the Petrine Primacy in the Roman pontiffs, the meaning and power of the papal primacy, and the infallible teaching authority (magisterium) of the Roman Pontiff.