According to Catholic teaching, the universal teaching body of the Church, when declaring unanimously to be an object of faith something relating to faith and morals, is endowed with _infallibility_, and also when in its daily practice of the faith it unanimously professes a doctrine to be a truth of faith. This infallibility is also possessed by the Pope alone when, acting in his capacity as Supreme Teacher of the Church in matters of faith and morals, he intends to give a permanent decision for the whole Church (ex cathedra). Besides these infallible teachings there are also _non-infallible_ teachings, and they are the more frequent. Such are, first of all, the ordinary doctrinal utterances of the Pope himself in his regular supervision of the teaching of doctrine: these instructions and declarations are of a lower kind than those peremptory ones that are pronounced ex cathedra: he is infallible only in the utterance of these ultimate, supreme decisions, the chief bulwark, as it were, erected against the floods of error. Decisions ex cathedra are very rare. Encyclical letters, too, are, as a rule, not infallible. It is self-evident that the theological opinions and statements of the Pope as a private person, not as Supreme Head of the Church, do not belong here at all. They have no official character and are in no way binding. Among decisions that are not infallible are further included, in various degrees, the doctrinal utterances of Bishops, of particular synods, and especially those of the Roman Congregations. The latter are bodies of Cardinals, delegated by the Head of the Church, as highest Papal boards, to co-operate with him in the various offices of administration. Of these, the Congregation of the Holy Office and that of the Index may also render decisions on doctrinal questions. Although the Congregations act by virtue of their delegation from the Pope, and publish their decrees with his consent, the decisions are not decisions of the Pope himself, but remain decisions of the Cardinals. Much less can the infallibility of the Pope pass over to them: it is his personal prerogative, the aid of the Holy Ghost is promised to him, and protects his judgments under certain conditions against error.