In a recent article, Emmet O’Regan has argued that the First Vatican Council not only defined dogmatically that the papal Magisterium is infallible under certain conditions but also “definitively excluded the possibility of a heretical pope” by elevating St. Robert Bellarmine’s “fourth proposition” to the “dignity of a dogma.” This article argues that when Pastor Aeternus is read in light of the official Relatio, it is clear that the council was not intending to exclude the possibility of a heretical pope, that is, the opinion of Albert Pighius. Instead, Gasser makes it clear that the council was intending to define what Bellarmine called the “most common and certain opinion,” which is “whether the pope is able to be a heretic or not, he is not able in any way to define a heretical proposition that must be believed by the whole Church.” O’Regan has misidentified which view of Bellarmine the council intended to define.