Any question in Papal Infallibility must relate to this text from the First Vatican Council. Notice right away that “infallibility” in this context is an abbreviation- the full concept one is speaking of is the infallible teaching authority of the pope. The most relevant passage in the discussion of this concept is its formal definition, which should be memorized by any Catholic seeking to do apologetics, along with the the relevent explanations and scriptural passages cited in the text above it. The Definition:
we teach and define as a divinely revealed dogma that
- when the Roman pontiff speaks EX CATHEDRA,
- that is, when,
- in the exercise of his office as shepherd and teacher of all Christians,
- in virtue of his supreme apostolic authority,
- he defines a doctrine concerning faith or morals to be held by the whole church,
- that is, when,
- he possesses,
- by the divine assistance promised to him in blessed Peter,
- that infallibility which the divine Redeemer willed his church to enjoy in defining doctrine concerning faith or morals.
- Therefore, such definitions of the Roman pontiff are of themselves, and not by the consent of the church, irreformable.
The immediate question that pops up is “what kind of authority does the Pope have when he is not speaking this way?” This question is answered by a careful consideration of the previous article (especially sec. 9), which describes the power and character of the Pope. Infallibility is a narrower aspect of the power set down in this article.
The basis or both article 3 and 4 is laid down in- you guessed it- sections 1 and 2.
As to the question raised about excommunication: excommunication is clearly a matter discipline and government of the church. Compare section 9 of article three with the third specification of the requirements for papal infallibility. Clearly, discipline and government have been left out. And so we conclude that this aspect of Papal authority is set apart from infallibility.
This raises the question of what the character of non-infallible actions are. Most persons have too narrow and shallow an understanding of this. A big reason for this is that they are reading section 4 apart form section 3. All Catholics are still disciples of the pontiff, and owe him deference before other teachers. Even when the Pope is not speaking infallibly, his teaching and his acts are still binding on all Catholics.
As to the Nazi question: any particular case of excommunication has to take into account prudential factors, and I don’t know enough about the situation described to speak to them. one thing to keep in mind about excommunication is that its grounding text is 1 Cor. chapter 5:
It is absolutely heard that there is fornication among you and such fornication as the like is not among the heathens: that one should have his father’s wife. 2 And you are puffed up and have not rather mourned: that he might be taken away from among you that hath done this thing. 3 I indeed, absent in body but present in spirit, have already judged, as though I were present, him that hath so done, 4In the name of our Lord Jesu Christ, you being gathered together and my spirit, with the power of our Lord Jesus: 5 To deliver such a one to Satan for the destruction of the flesh, that the spirit may be saved in the day of our Lord Jesus Christ
Pay particular attention to verse five. We excommunicate the person for his own sake, that he might repent. There are obviously other reasons too, but this one is included in them. To simply excommunicate without at least considering the interests of the one to be excommunicated is unscriptural and therefore against the faith. This might provide a certain light to seeing why the Holy Church excommunicates some people for what seem like lighter crimes, and fails to excommunicate others for far more dire crimes. There is more than simply the severity of the crime to take into account.