Those who claim that Pope Francis has or might fall into heresy or teach heresy sometimes support their claim by citing past Popes who supposedly did the same.
Pope Honorius I is often accused of heresy, but the accusation is false. Honorius I was Roman Pontiff from 625 to his death in 638. The Third Council of Constantinople, which is the Sixth Ecumenical Council overall, was held from 680 to 681. Over 40 years after his death, the Council excommunicated Honorius I and declared him a heretic.
The situation faced by Honorius I was complex. The eventual decision of the Church, infallibly taught by the Third Council of Constantinople, was that Christ has two wills, one for each of His two natures: human and Divine. But during the time of Honorius, the Magisterium had not yet decided the question of whether Christ has one will or two. And though every Pope can exercise the Magisterium (the teaching authority of the Church), every Pope is also subject to that teaching. At that time, it was an open question. The Pope was unsure of the correct doctrine, as is clear from his private letters to some Bishops. But he never exercised the Magisterium to teach either way.
The Church has two types of authority: the teaching authority (doctrine) and the temporal authority (discipline). The teaching authority, or Magisterium, can teach infallibly (no possibility of error) or non-infallibly (limited possibility of error). Each Ecumenical Council has the full authority of the Church over both doctrine and discipline. A Council can teach infallibly or teach non-infallibly, or decide matters of discipline (rules and rulings). A Council can do some or all of these things. Of the 21 Ecumenical Councils so far, some only exercised authority over discipline and did not teach at all.
Moreover, not every teaching of every Council is infallible. The Second Vatican Council, for example, issued many non-infallible teachings. But the decision of an Ecumenical Council to excommunicate someone and/or to declare someone a heretic is of the temporal authority of the Church. Such a decision is of the fallible temporal authority; it is neither infallible, nor non-infallible. Was the decision of the Council, to call Honorius I a heretic and to excommunicate him, infallible? Not, it was not. So the Council could have erred in that regard.
The next Pope to reign after the Third Council of Constantinople was Leo II (682 to 683). Pope Leo II condemned Pope Honorius I, not for teaching any heresy, but for failing to decide the question and failing to refute the false idea that Christ has only one will. The Catholic Encyclopedia says, about this decision of Pope Leo:
“At the same time he was at pains to make it clear that in condemning his predecessor Honorius I, he did so, not because he taught heresy, but because he was not active enough in opposing it.”
The problem with the Council’s claim that Honorius I was a heretic is that the question of Christ’s wills was undecided by the Magisterium at the time. Honorius can be blamed for not doing more to stem the spread of this error, but since the Magisterium at the time had no infallible teaching on the subject, he is not properly accused or convicted of heresy. So the Council erred in calling Honorius I a heretic, as the subsequent decision of Pope Leo II makes clear.
Pope Honorius I never taught the heresy that Christ only has one will. He also was personally undecided on the question, as is clear from his letters to Bishops. By not deciding the question against those who believed in only one will for Christ, he harmed the Faith by his negligence. But Christ never promised that Peter and His successors would be sinless or free from all error in their decisions. He only promised that their faith would not fail, and that the Church led by each Pope would remain indefectible.
Was Saint Thomas Aquinas, Doctor of the Church, a heretic for denying the sanctification of the Blessed Virgin Mary in the first moment of her Immaculate Conception? No, he was not a heretic. For at the time, the Magisterium had not yet infallibly taught the dogma of the Immaculate Conception. It was at the time an open question. Pope Honorius I reigned in a time before the Church had decided the question of the two wills of Jesus Christ.
[The above text is quoted from my book: In Defense of Pope Francis]
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