Sedeprivationism is a doctrinal position within Traditionalist Catholicism which holds that the current occupant of the Holy See is a duly-elected pope, but lacks the authority and ability to teach or to govern unless he recants the changes brought by the Second Vatican Council.
[1] The doctrine asserts that since this council, occupants of the See of Peter are popes materialiter sed non formaliter, that is "materially but not formally".
The doctrine of Sedeprivationism traces its origin to the Thesis of Cassiciacum of the Dominican Catholic theologian Michel-Louis Guérard des Lauriers.
[citation needed] The Thesis of Cassiciacum, which asserts the position of sedeprivationism, states that the See of Peter is not obtained and must conform with one of two prescribed requirements of a legitimate papal election by the popes: The Thesis of Cassiciacum, as held by the Istituto Mater Boni Consilii and others, contends that both aspects are required and that if any candidate fails either one, he would not be elected to the office of pope.
The Catholics adhering to the thesis hold that all claimants of the papal office from at least Paul VI to Francis are invalid and do not hold the papal office except by right of designation because of a failure to receive the form of the papacy (i.e. the authority) because his acceptance is impeded by a defective intention[8] arising from their manifest disposition of apostasy.
This is contrasted with the position of sedevacantism, which asserts a vacancy in the papal office; the term sede vacante means "empty chair" in reference to the See of Saint Peter.