The accurate treatment of this question is no less necessary than arduous, because of the daily illusions even of spiritual persons. In deciding it I shall follow the footsteps of others, who have run together in rivalry to roll this stone. The chief were Blessed Vincent Ferrer, in his treatise On the Spiritual Life, chapters 11 and 12; John Gerson, in his treatise On the Approval of Spirits, and elsewhere throughout; Cardinal Torquemada, in the preface to the Defense of the Revelations of Blessed Bridget; Henry of Firmaria, in the book On the Four Instincts; Aegidius Carlerius, in the first part of the Bundle of Fragments, at the beginning; Jerome of Ferrara, in the Compendium of Revelations; Giovanni Francesco Pico, in the last book On Foreknowledge; Ribadeneyra, in the book On Tribulation, chapter 15; and others, including certain more recent writers, all of whose sayings you will find in those older writers.
All things can be reduced to three heads: the one who judges, the person to whom the revelation has been made, and the revelation itself together with its circumstances. Let us look at each.
[margin: Vincent Ferrer, On the Spiritual Life, chapters 11-12; Gerson, On the Approval of Spirits; Torquemada, preface to the Defense of the Revelations of Blessed Bridget; Henry of Firmaria; Aegidius Carlerius; Jerome of Ferrara; Giovanni Francesco Pico, final book On Foreknowledge; Ribadeneyra, On Tribulation, chapter 15]