Pope St. Marcellinus offered incense to an idol, though he repented of it later. Was the chair vacant between the time he apostasized and repented?
Pope St. Gregory XVII said in a letter to some muslim ruler that Christians and muslims worship the same god. Was he an antipope according to some sedes' standards? How is he a saint then?
Pope St. Pius X and Pope Pius XII both did liturgical reforms. If Quo Primum was truly binding then does that mean that these popes were heretics?

If a pope becomes a heretic, either publicly or privately, does he lose his office? Does he have to profess material "accidental" heresy or formal obstinate heresy in order to be severed from the Church? I'm not sure exactly  Pope Pius XII meant in his encyclical  Mystici Corporis:

For not every sin, however grave it may be, is such as of its own nature to sever a man from the Body of the Church, as does schism or heresy or apostasy. Men may lose charity and divine grace through sin, thus becoming incapable of supernatural merit, and yet not be deprived of all life if they hold fast to faith and Christian hope, and if, illumined from above, they are spurred on by the interior promptings of the Holy Spirit to salutary fear and are moved to prayer and penance for their sins.

 ....or is he still a valid pope that,  though in the eyes of God he may lose membership from the church, is still the authority of the Church? Is it possible for a pope to become severed from the Church due to heresy, yet have his office remain valid (so that he can pronounce dogmas, canonize, etc)? Also, the First Vatican Council stated that it was impossible for a council to be set up to judge a pope, yet how did a council condemn Pope Honorius 1?

The sentence of the Apostolic See (than which there is no higher authority) is not subject to revision by anyone, nor may anyone lawfully pass judgment thereupon. And so they stray from the genuine path of truth who maintain that it is lawful to appeal from the judgments of the Roman pontiffs to an ecuмenical council as if this were an authority superior to the Roman Pontif.”? Id, Ch. 3, sec. 8.

And one FINAL question. What do you think of the idea that theres has never been a heretical pope? Some traditonal websites like NovusOrdoWatch and Our Lady of the Rosary Library( quoting from Micahel Davies) say that there never has been a pope whowas a heretic. Although history seems to contradict this assertion..

Thank you. I am not looking for heated arguments by the way, JUST looking for your opinions. So please don't get carried away

If you can't find a source for your claim regarding St. Gregory VII, I for one have nothing to say about it, for claims presented without evidence are dismissed without evidence.

There has never been a heretical pope.  The claim that there was has been used by Protestants and Gallicans to attack papal infallibility, and the Fathers of Vatican I systematically refuted every such charge raised.

Quote from: Mercyandjustice

Pope St. Marcellinus offered incense to an idol, though he repented of it later. Was the chair vacant between the time he apostasized and repented?
Pope St. Gregory XVII said in a letter to some muslim ruler that Christians and muslims worship the same god. Was he an antipope according to some sedes' standards? How is he a saint then?
Pope St. Pius X and Pope Pius XII both did liturgical reforms. If Quo Primum was truly binding then does that mean that these popes were heretics?

If a pope becomes a heretic, either publicly or privately, does he lose his office? Does he have to profess material "accidental" heresy or formal obstinate heresy in order to be severed from the Church? I'm not sure exactly  Pope Pius XII meant in his encyclical  Mystici Corporis:

Quote

For not every sin, however grave it may be, is such as of its own nature to sever a man from the Body of the Church, as does schism or heresy or apostasy. Men may lose charity and divine grace through sin, thus becoming incapable of supernatural merit, and yet not be deprived of all life if they hold fast to faith and Christian hope, and if, illumined from above, they are spurred on by the interior promptings of the Holy Spirit to salutary fear and are moved to prayer and penance for their sins.

 ....or is he still a valid pope that,  though in the eyes of God he may lose membership from the church, is still the authority of the Church? Is it possible for a pope to become severed from the Church due to heresy, yet have his office remain valid (so that he can pronounce dogmas, canonize, etc)? Also, the First Vatican Council stated that it was impossible for a council to be set up to judge a pope, yet how did a council condemn Pope Honorius 1?

Quote

The sentence of the Apostolic See (than which there is no higher authority) is not subject to revision by anyone, nor may anyone lawfully pass judgment thereupon. And so they stray from the genuine path of truth who maintain that it is lawful to appeal from the judgments of the Roman pontiffs to an ecuмenical council as if this were an authority superior to the Roman Pontif.”? Id, Ch. 3, sec. 8.

And one FINAL question. What do you think of the idea that theres has never been a heretical pope? Some traditonal websites like NovusOrdoWatch and Our Lady of the Rosary Library( quoting from Micahel Davies) say that there never has been a pope whowas a heretic. Although history seems to contradict this assertion..

Thank you. I am not looking for heated arguments by the way, JUST looking for your opinions. So please don't get carried away

Don't go any farther down this road, please. You'll end up like another Richard Ibranyi if you do.

God forbid! His beliefs are crazy and irrational. I went on his website and saw photos of his little cult and was surprised. He had images of our Lady of Grace, Guadalupe. The Sacred and Immaculate hearts, St Joseph statue, etc. If he believes that the Church ceased to exist in the 1100s, then why does he have images of latter day devotions? By my original post I was  just trying to figure out if a pope can be a heretic, and if so to what extent. Right now I don't think a pope can be a heretic...