The Vatican I dogma on papal infallibility declares:
Vatican I (
Pastor Aeternus, Chap 4, #9, an infallible dogma) is the basis for understanding infallibility.
“9. Therefore, faithfully adhering to the tradition received from the beginning of the Christian faith, to the glory of God our saviour, for the exaltation of the Catholic religion and for the salvation of the Christian people, with the approval of the Sacred Council, 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, 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.
“So then, should anyone, which God forbid, have the temerity to reject this definition of ours: let him be anathema.”
papalencyclicals.net/Councils/ecum20.htm
ANATHEMA. Solemn condemnation, of biblical origin, used by the Church to declare that some position or teaching contradicts Catholic faith and doctrine.
Modern Catholic Dictionary by Fr. John A. Hardon, S.J.
therealpresence.org/cgi-bin/getdefinition.pl
For infallibility to be exercised the Pope must teach:
(a) ex cathedra (from the Chair of Peter), that is as Shepherd and Teacher of all Christians,
(b) speaking with Peter’s apostolic authority to the whole Church,
(c) defining a doctrine of faith and morals.
Therefore only dogmas or definitive doctrinal teachings are infallible, not arguments nor any other declarations outside of definitive statements.
With the 1997 update of the CCC, # 88 reads: “The Church’s Magisterium exercises the authority it holds from Christ to the fullest extent when it defines dogmas, that is, when it proposes truths contained in divine Revelation or having a necessary connection with them, in a form obliging the Christian people to an irrevocable adherence of faith, or also when it proposes in a definitive way, truths having a necessary connection with these.”