The claim that under certain conditions the doctrinal and moral teaching of a Church cannot err applies particularly to the Roman Catholic Church and to the Pope. Infallibility is derived from the belief that God has intervened in human history and has given man the possibility of assurance in religious matters; also from the belief that the Church is not a human creation, its essential structure and nature having been determined by Christ. The Church is seen as the extension of Christ in time, and the Pope as the Supreme teacher in the Church, guided by Christ. Papal declarations may be strongly adhered to, particularly by members of traditional or underdeveloped societies and this may retard social progress (for example, with birth control and abortion). The Roman Catholic claims to the primacy of the bishopric of Rome among bishops, and the infallibility of ex cathedra teachings, are the major impediments to ecumenicism and Church reunification.
The papal and magisterial errors errors fall into four main areas:
1. Theological errors taught by popes or central Roman authorities, including: declaration that it is necessary for salvation for every human person to be subject to the bishop of Rome (Boniface VIII, 1302); declaration that the 1590 version of the Vulgate (riddled with errors) was forever valid and unalterable (Sixtus V, 1590), although it had to be replaced within two years; variety of statements made by the Pontifical Bible Commission (1906-1933) subsequently rejected by all or most Catholic Biblical scholars.
2. Moral teachings which have been later reversed or ignored, including those on: slavery, usury, contraception and family planning, and prohibition of sex during menstruation.
3. Errors of moral action or insight by Rome, whether popes or officials, including: calling for the Crusades (Urban II); allowing the use of torture by the Inquisition (Gregory IX); calling for the ghettoization of Polish Jews (Benedict XIV); papal attacks on the availability of the Bible to the laity.
4. Errors of moral action by Councils, including: anathematizing women who cut off hair (Gangra, 325-381); imposition of symbol on the Jews (Lateran VI, 1215).
The historical church can never claim to be infallible or inerrant in regard to any of its decisions or traditions, for all of them are relative to historical conditions. Even the relative authority which can be claimed for a decision or tradition will depend upon its adherence to the mandate: "As the Father has sent me, even so I send you".
Some of the "errors" cited, do not logically at least, invalidate claims to magisterial or papal infallibility. The main defense would be that the error was not "asserted as infallible", or that the person making the error was acting in an unofficial capacity.