But I have a question for you, since not all sins sever like heresy or schism (Mystici Corporis). How then are they different? Anyone in sin, any mortal sin, has lost the bond with Christ (the spiritual bond) as a result of losing his justification. Are you saying there is no difference with the sin of heresy or schism? I think Pius XII is clearly saying there is. So what's the difference?
Hey DR. If I understand your question correctly, the difference is that with apostasy, heresy and schism it is the nature of the sin that leads to exclusion from the Church, whereas with some other grave sins it is the disciplinary action of the Church authority excommunicating.
Canon George Smith explains in The Teaching of the Catholic Church, p707:
Nevertheless, the melancholy possibility must be envisaged of those who may have "cut themselves off from the structure of the Body by their own unhappy act or been severed therefrom, for very grave crimes, by the legitimate authority." (Quoting MCC)
In other words, the Church, as being a perfectly constituted society, has the right for grave reasons of excluding from membership. She may pass sentence of, or lay down conditions which involve, excommunication. This carries with it the deprivation of rights and privileges enjoyed by those in communion with the faithful. But such a juridical penalty does not wholly nullify membership of the Church, still less does it necessarily imply the final condemnation before God of the excommunicated person.
Certain sins - viz., apostasy, heresy and schism - of their nature cut off the guilty from the living Body of Christ. Apostasy is a form of spiritual ѕυιcιdє, being the complete and voluntary abandonment of the Christian faith which one once professed. Heresy, objectively considered, is a doctrinal proposition which contradicts an article of faith; from the subjective point of view it may be defined as an error concerning the Catholic faith, freely and obstinately persisted in by a professing Christian... It can hardly be denied that those who take up any of these propositions - most evidently is this the case with the deliberate apostate - sever themselves by their own act from membership of the Church.
"It can hardly be denied" - of course, it is obvious. This is not a new teaching of
Mystici Corporis, as you and I both know, DR. It is just restating common Catholic sense. It was equally obvious to Cajetan, Bellarmine, Suarez, Billuart, Garrigou-Lagrange... This contributes nothing to the theological debate as to how a heretic Pope is deposed, nor how he loses jurisdiction. It is sheer nonsense to maintain that
MCC in any way addresses, let alone resolves, this age-old theological controversy.