A revelation is a priori probable. Its probability is suggested by our ignorance, which is only too keenly felt. For no sane man would say, I am so clever, I am above being beholden to the aid of a teacher. Hence it is a priori probable that the Creator has supplied, by some special communication, what He has left imperfect in our means of discovering truth for ourselves. Probably He has made an external revelation the complement of inner incompleteness.
Circumstances thus show the likelihood of a revelation.
As taught by the revelation which we have actually received, we know that in view of the strictly supernatural end to which de facto we are destined, revelation is not merely a matter of more convenient provision, but an absolute necessity.