That doubtless is true, when there is question of facts which are necessary or useful as a basis for religion, in which case the revelation is accompanied by proofs that guarantee its accuracy. A vision need not guarantee its accuracy in every detail. One should thus beware of concluding without examination that revelations are to be rejected; the prudent course is neither to believe nor to deny them unless there is sufficient reason for so doing. Much less should one suspect that the saints have been always, or very often deceived in their vision. On the contrary, such deception is rare, and as a rule in unimportant matters only. There are cases in which we can be certain that a revelation is Divine. (1) God can give this certainty to the person who receives the revelation (at least during it), by granting an insight and an evidence so compelling as to exclude all possibility of doubt. We can find an analogy in the natural order: our senses are subject to many illusions, and yet we frequently perceive clearly that we have not been deceived. (2) At times others can be equally certain of the revelation thus vouchsafed. For instance, the Prophets of the Old Testament gave indubitable signs of their mission; otherwise they would not have been believed. There were always false prophets, who deceived some of the people but, inasmuch as the faithful were counselled by Holy Writ to distinguish the false from the true, it was possible so to distinguish. One incontrovertible proof is the working of a miracle, if it be wrought for this purpose and circumstances show this to be so. A prophecy realized is equally convincing, when it is precise and cannot be the result of chance or of a conjecture of the evil spirit. Besides these rather rare means of forming an opinion, there is another, but longer and more intricate method: to discuss the reasons for and against. Practically, this examination will often give only a probability more or less great. ...
