Oath Against Modernism

The Oath Against Modernism was instituted by Pope Pius X in his motu proprio Sacrorum antistitum on September 1, 1910. The oath was required of "all clergy, pastors, confessors, preachers, religious superiors, and professors in philosophical-theological seminaries" of the Catholic Church. It remained in force until the Congregation for the Doctrine of the Faith, with the approval of Paul VI, replaced it with a revised Profession of Faith on July 17, 1967.

The oath marked the culmination of Pius X's campaign against the theological movement of Modernism, which he extensively analyzed and denounced as heretical in his 1907 encyclicals Pascendi Dominici gregis and Lamentabili sane exitu. Thomas Pègues, O.P., was also influential in the anti-modernist movement within the Church.

The Oath Against Modernism is still pronounced by the Society of Saint Pius X, and sedeprivationist and sedevacantist groups such as the Congregation of Mary Immaculate Queen and the Istituto Mater Boni Consilii.