1. Concerning SSPX.

Responsa from Vatican congregations hold the weight of authority. The faithful are bound under pain of the mortal sin of temerity to submit to these decisions with religious submission of mind and will.
2. This means that they have legitimate authority and that the “benefit of the doubt” should be given to them, and they should be obeyed under normal circumstances
3. Under extraordinary circumstances these legitimate authorities may be disobeyed but only under extraordinary circumstances. Otherwise, it is the sin of temerity, which is an imprudence whereby a man dismisses grave counsel from a legitimate authority
4. An extraordinary circumstance is, for example if, God forbid, such a congregation commanded any one of the faithful to commit a sin. Or if a member of the faithful had a manifestly grave cause to remove his assent from the answer of a congregation (this is noted by Ott)
5. Ecclesia Dei, the Vatican congregation (formerly) responsible for Qs re: SSPX, has clarified certain matters. Thus these decisions cannot be disobeyed unless a member of the faithful has a manifestly grave cause to do so. Anyone who denies these must prove grave cause.
6. Among the matters clarified by this Vatican congregation are the following:

-The SSPX is not in formal schism

-Holy communion at an SSPX Mass SOLELY for the purpose of hearing Mass with the 1962 Missal is NO SIN WHATSOEVER.
7.

-The faithful can tithe to the SSPX

-However, the Vatican officially discourages the faithful from attending the SSPX in order to avoid a “schismatic attitude”
8. Thus, according to an objective standard of assent, no one can deny the above without some grave cause.
9. My opinion: it would seem that one area of legitimate debate is whether the faithful can commune at SSPX even if there is a diocesan Latin Mass available.
My opinion: Under the norms of Summorum Pontificum, a coetus of the faithful have a right to the Latin Mass. Therefore according to Ecclesia Dei those faithful who seek the Latin Mass can commune at an SSPX chapel - esp. if their bishop disobeys Summorum - with no sin whatsoever
All sources for these assertions can be found in this video with the notes:
It is important to note as well that the assertions above are given with reference to the church functioning under ordinary circumstances. extraordinary circumstances can necessitate a different course of action. The SSPX has maintained that we are in such a circumstance
You can follow @meaningofcath.
Tip: mention @twtextapp on a Twitter thread with the keyword “unroll” to get a link to it.

Latest Threads Unrolled: