The Roman Pontiff is the only Supreme Pontiff on earth who is guaranteed to be free from material and formal heresy at all times. The body of Bishops, as long as they remain in communion with and in obedience to the Roman Pontiff also have this same charism of truth and of never-failing faith, which preserves them also from every grave failing in faith and every grave error on doctrine and discipline, just as the Pope is preserved from the same. But the Bishops are protected from these errors and failings in faith only as a body, not as individuals.
Since the Roman Pontiff has the supreme authority Christ gave to Peter, over doctrine and discipline, since he is the supreme judge of all the faithful, since he has the charism of truth and of never-failing faith and so can never err gravely in doctrine or discipline and can never fail in faith, the Roman Pontiff is therefore the only sure judge (along with any Ecumenical Council approved by the Pope) over heresy and heretics.
No Roman Pontiff has ever and can ever teach material heresy, nor commit formal heresy. For the charism of truth protects him from teaching heretical falsehoods even inadvertently. Mere material heresy, taught without moral culpability, is still contrary to truth itself. And the charism of never-failing faith protects him from formal heresy. For though the Pope can sin mortally in many different ways, yet the prevenient grace of God protects him from every grave failure of faith, not for his sake, but for the sake of the Church and the path of salvation of the faithful.
Whatever is condemned by any Roman Pontiff as heresy, even without a formal definition, is certainly heresy, as the Pope cannot err gravely in what is non-infallible, nor at all in what is infallible. Then the teachings of every Roman Pontiff which are proclaimed definitively are infallible, even without a formal definition. This is clear from past Ecumenical Councils, which often settled controversies by condemning heresies and teaching the contrary dogma, but in paragraph form and without a discrete definition. Then, when we consider the infallible teachings of Jesus himself, and of the New Testament more generally, the innumerable infallible truths expressed therein do not require a particular exterior form of language in order to be understood to be dogmas of the Faith.
Popes have taught infallibly thousands and thousands of times, not just a handful of times. And every definitive teaching of every Ecumenical Council is entirely without error on faith or morals. For the decisions of the Roman Pontiff and the body of Bishops teaching the whole world on important matters of faith and morals is certainly definitive.
Those who claim that any Roman Pontiff has erred gravely on doctrine or discipline are contradicting the infallible teachings of the perennial Magisterium (infallible under the ordinary universal Magisterium) and the dogmas of the First Vatican Council. Those who accuse Pope Francis or other Popes of heresy are themselves heretics. And who would submit their mind and heart to the Roman Pontiff, if they also think that the same Pontiff is a heretic? So those who accuse the Pope of heresy — whether material or formal — are also schismatics.
A Catholic may faithfully disagree, mildly and occasionally, with a non-infallible teaching of the Magisterium. But we can never accuse any Pope or Council of grave error on doctrine or discipline; never accuse Popes or Councils of heresy, apostasy, or idolatry; and never claim that the Church has gone astray or led astray by any decision of doctrine or discipline, including on the liturgy of the holy Mass.
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