Assertion 5:
The Church's infallibility extends to the canonization of saints. This is the common opinion today. (19)
Canonization (formal) is the final and definitive decree by which the sovereign pontiff declares that someone has been admitted to heaven and is to be venerated by everyone, at least in the sense that all the faithful are held to consider the person a saint worthy of public veneration. It differs from beatification, which is a provisional rather than a definitive decree, by which veneration is only permitted, or at least is not universally prescribed.
Infallibility is claimed for canonization only; (20) a decree of beatification, which in the eyes of the Church is not definitive but may still be rescinded, is to be considered morally certain indeed, but not infallible. Still, there are some theologians who take a different view of the matter.
Proof:
1.
From the solid conviction of the Church. When the popes canonize, they use terminology which makes it quite evident that they consider decrees of canonization infallible. Here is, in sum, the formula they use: “By the authority of our Lord Jesus Christ and of the apostles Peter and Paul and by our own authority, we declare that N. has been admitted to heaven, and we decree and define that he is to be venerated in public and in private as a saint.”
2.
From the purpose of infallibility. The Church is infallible so that it may be a trustworthy teacher of the Christian religion and of the Christian way of life. But it would not be such if it could err in the canonization of saints. Would not religion be sullied if a person in hell were, by a definitive decree, offered to everyone as an object of religious veneration? Would not the moral law be at least weakened to some extent, if a protégé of the devil could be irrevocably set up as a model of virtue for all to imitate and for all to invoke? But it cannot be inferred: therefore the Church must also be infallible in authenticating the relics of the saints; for (a) the Church never issues so solemn a decree about relics; and (b) the cases are not parallel, for in the case of relics, it is a question of relative cult, while in that of the saints it is one of absolute cult.(21)
Corollory
Several considerations urge the conclusion that the Church's infallibility extends also to equivalent canonization, formerly quite common. By this means, without any formal decree of canonization, a deceased person gradually came to be venerated by the universal Church. However, formal and equivalent canonizations arc not at all on the same plane; in the latter the consent of the supreme pontiff can be taken as purely permissive, in much the same way as the veneration of a beatified person is sometimes permitted the universal Church. Some scholars are led by this observation to think that it is not absolutely impossible that someone who is not a saint might appear among those who, without being formally canonized, have a commemoration or even a full office in the Breviary. The papal approval of the Breviary, they say, as far as they who have not been formally canonized are concerned, amounts to nothing more than an order that no change be made therein. This is not a definitive decree, but rather permission to continue the traditional cult.(22)
Scholion: Is the fact of the Church's infallibility in matters related to revealed truth itself a revealed truth?
In each instance we have proved the infallibility of the Church's teaching office in matters related to the deposit of revelation from the express purpose of infallibility and from the mind of the Church. It is, consequently, clear that this infallibility is at least a conclusion from revelation; indeed a conclusion whose validity the Church itself has sanctioned at least by its practical attitude and mode of action. But serious reasons incline us to state that this extension of infallibility — not of course to each of the items considered individually above, but to related matters in general — is a formally revealed truth. There is no doubt that our Lord promised His Church the “Spirit of truth” (John 14:17), who would teach “the whole range of truth” (John 16:13); the apostle calls the Church the pillar and bulwark of truth (I Tim. 3:15).(23) What, then, does the word “truth” or the phrase “the whole range of truth” mean in these texts: just revealed truth, or all the truth which the Church, in view of its special purpose, must know with certainty? The answer seems to be that since the terms are general, and the purpose of the Church militates against their being restricted to revealed truths, they must doubtless be understood as referring to all doctrines which concern Christian faith and morality either directly or indirectly. In other words, they must include also matters connected with revealed truth.
This is why Cardinal Franzelin could in the following way describe the general proposition of infallibility in related matters: this assertion, “as all theologians agree, is so certain that its denial would be an error, or even, in the opinion of many, a heresy, even though it has not as yet been explicitly condemned as heretical.”(24)
Full text found
HERE(Monsignor G. Van Noort, S.T.D., Dogmatic Theology, Volume II, Christ's Church, Translated and Revised by John J. Castelot, S.S., S.T.D., S.S.L. & William R. Murphy, S.S., S.T.D., The Newman Press, Westminster, Maryland, 1957. pp 102-124.)