First of all, when the question arises concerning the infallibility of canonization, it usually centers on the action of a pope officially declaring someone to be a saint. There is debate among theologians as to whether or not papal infallibility extends to this, but according to the Catholic Encyclopedia most theologians believe that it does (for more information, please visit
this link and scroll down to the heading, “Papal Infallibility and Canonization”). However, in the early Church, awarding someone the title of “saint” was not a formal process but rather resulted from public acclamation. In those days, there were no official canonization investigations or papal declarations on the matter, and therefore the question of papal infallibility does not enter into it.
Concerning the saints of the early Church, our historical knowledge of some of them has considerably dwindled over time, and it is often hard to distinguish between facts and what are called “pious legends”. The historical authenticity of information conveyed through pious legends can be questionable because such accounts are subjected to the phenomena described in the opening section of this article:
Literary or Profane Legends. Generally speaking, it is not that the very existence of such saints is doubted, but that there may be a notable distinction between the actual holy people who walked the earth and many of the stories that developed concerning them. A pious legend told about a saint may or may not be true, but such information is not doctrinal, nor do popes make solemn pronouncements concerning such things. In light of all this, even if certain elements of the pious legend of a saint are fictional, it does not call into question the Church’s power of infallibility.
When you commented that you heard that certain saints have been “removed”, I presume that you are referring to the fact that the Church has removed the feast days of such saints from the liturgical calendar. For an elaboration on this type of situation (and what it means), please read:
Is Saint Christopher No Longer a Saint?
Finally, I am aware of at least one situation in which the actual existence of a saint is, indeed, seriously called into question by a number of historians, and this is the case involving
St. Philomena. Consider, for example, these exchanges from EWTN’s website:
St. Philomena question from 8/29/2001
St. Philomena question from 10/7/2002
St. Philomena question from 2/28/2002
Although in 1837 Pope Gregory XVI dedicated a feast day for St. Philomena and certain popes promoted devotions to her, it is my understanding that they were simply acting under the impression that she was an ancient Christian martyr (and therefore considered a saint of the early Church). This is, after all, what some of the historical evidence at the time suggested. Note that merely endorsing devotion to a saint is not an infallible statement about the existence of said person.
As a side note, although in recent times the Church has suppressed aspects involving devotion to St. Philomena (as described in the above linked information from EWTN), she has not been “de-canonized” (as some incorrectly describe the situation).
