In my opinion, the following papal statement meets all of the criteria for papal infallibility:
“Wherefore, in order that all doubt may be removed regarding a matter of great importance, a matter which pertains to the Church’s divine constitution itself, in virtue of my ministry of confirming the brethren (cf. Lk 22:32) I declare that the Church has no authority whatsoever to confer priestly ordination on women and that this judgment is to be definitively held by all the Church’s faithful.”
But that opinion is a matter of some dispute; some say that it is infallible, but for other reasons.
Five criteria are required, but your sentence only had three:
- when the Holy Father
- invokes his authority as chief teacher
- in regards to matters of doctrine and morals…
- should be “by a definitive act, he proclaims” or in other words “he defines”
and
- should be that the doctrine “must be held by the whole Church”
So the statement from OS does meet all 5 criteria, but not every papal teaching meets all 5 criteria. If the Pope is just teaching by virtue of his authority as Pope, that constitutes the first two criteria, and often the fourth criteria will be met, if it is on faith and morals (or any teaching from Divine Revelation, i.e. Tradition and Scripture).
But the third and fifth criteria are the ones most often absent.
Papal teachings are not usually definitions of doctrine (“he defines”), and they often do not bind the universal Church. The Pope often teaches without saying to the faithful, in efffect, ‘you must believe each and every sentence of what I am saying.’
So papal teachings do not usually fall under papal infallibility.
Ron