A recent question on the Medieval Religion discussion group as to whether canonisations are infallible acts of the Pope elicited this response from Fr Paul Chandler, who is a Carmelite in Australia, and which I thought might be of interest to readers:
Until recently it was indeed the general opinion of theologians that canonizations are infallible. There were dissenting opinions, however: Augustine of Ancona (1243-1328) held that it was impossible to judge definitively the state of a person's conscience and that canonization could not therefore be infallible. Cajetan (1469-1534) held a similar position.
In recent times there has been controversy (see, for example, Francis A. Sullivan's treatment in Magisterium (1983)), a disagreement which extends into the Vatican's Congregation of Saints, where officials have argued contradictory positions (Daniel Ols, “Fondamenti teologici del culto dei Santi,” in Dello Studium Congregationis de causis sanctorum, pars theologica (Rome, 2002): 1-54.
The traditional opinion is summed up pretty fairly in the old Catholic Encyclopedia (1913).
Is the pope infallible in issuing a decree of canonization? Most theologians answer in the affirmative. It is the opinion of St. Antoninus, Melchior Cano, Suarez, Bellarmine, Bañez, Vasquez, and, among the canonists, of Gonzales Tellez, Fagnanus, Schmalzgrüber, Barbosa, Reiffenstül, Covarruvias (Variar. resol., I, x, no 13), Albitius (De Inconstantiâ in fide, xi, no 205), Petra (Comm. in Const. Apost., I, in notes to Const. I, Alex., III, no 17 sqq.), Joannes a S. Thomâ (on II-II, Q. I, disp. 9, a. 2), Silvester (Summa, s.v. Canonizatio), Del Bene (De Officio Inquisit. II, dub. 253), and many others. In Quodlib. IX, a. 16, St. Thomas says: "Since the honour we pay the saints is in a certain sense a profession of faith, i.e., a belief in the glory of the Saints [quâ sanctorum gloriam credimus] we must piously believe that in this matter also the judgment of the Church is not liable to error." These words of St. Thomas, as is evident from the authorities just cited, all favouring a positive infallibility, have been interpreted by his school in favour of papal infallibility in the matter of canonization, and this interpretation is supported by several other passages in the same Quodlibet. This infallibility, however according to the holy doctor, is only a point of pious belief. Theologians generally agree as to the fact of papal infallibility in this matter of canonization, but disagree as to the quality of certitude due to a papal decree in such matter. In the opinion of some it is of faith (Arriaga, De fide, disp. 9, p. 5, no 27); others hold that to refuse assent to such a judgment of the Holy See would be both impious and rash, as Francisco Suárez (De fide, disp. 5 p. 8, no 8); many more (and this is the general view) hold such a pronouncement to be theologically certain, not being of Divine Faith as its purport has not been immediately revealed, nor of ecclesiastical Faith as having thus far not been defined by the Church.
What is the object of this infallible judgment of the pope? Does he define that the person canonized is in heaven or only that he has practiced Christian virtues in an heroic degree? I have never seen this question discussed; my own opinion is that nothing else is defined than that the person canonized is in heaven. The formula used in the act of canonization has nothing more than this:
"In honour of . . . we decree and define that Blessed N. is a Saint, and we inscribe his name in the catalogue of saints, and order that his memory by devoutly and piously celebrated yearly on the . . . day of . . . his feast."
(Ad honorem . . . beatum N. Sanctum esse decernimus et definimus ac sanctorum catalogo adscribimus statuentes ab ecclesiâ universali illius memoriam quolibet anno, die ejus natali . . . piâ devotione recoli debere.)
There is no question of heroic virtue in this formula; on the other hand, sanctity does not necessarily imply the exercise of heroic virtue, since one who had not hitherto practised heroic virtue would, by the one transient heroic act in which he yielded up his life for Christ, have justly deserved to be considered a saint. This view seems all the more certain if we reflect that all the arguments of theologians for papal infallibility in the canonization of saints are based on the fact that on such occasions the popes believe and assert that the decision which they publish is infallible (Pesch, Prael. Dogm., I, 552).
This general agreement of theologians as to papal infallibility in canonization must not be extended to beatification, not withstanding the contrary teaching of the canonical commentary known as "Glossa" [in cap. un. de reliquiis et venerat. SS. (III, 22) in 6; Innocent., Comm. in quinque Decretalium libros, tit. de reliquiis, etc., no 4; Ostiensis in eumd. tit. no 10; Felini, cap. lii, De testibus, etc., X (II, 20); Caietani, tract. De indulgentiis adversus Lutherum ad Julium Mediceum; Augustini de Ancona, seu Triumphi, De potestate eccl., Q. xiv, a. 4). Canonists and theologians generally deny the infallible character of decrees of beatification, whether formal or equivalent, since it is always a permission, not a command; while it leads to canonization, it is not the last step. Moreover, in most cases, the cultus permitted by beatification, is restricted to a determined province, city, or religious body (Benedict XIV, op. cit., I, xlii). Some, however, have thought otherwise (Arriaga, Theol., V, disp. 7, p. 6; Amicus, Theol., IV, disp. 7, p. 4, no 98; Turrianus on II-II, V, disp. 17, no 6; Del Bene, De S. Inquisit. II, dub. 254).
Beccari, Camillo. "Beatification and Canonization." The Catholic Encyclopedia Vol. 2. New York: Robert Appleton Company, 1907. 4 Jul. 2015