The Certainty of Nathaniel
“Faith derives its certitude from outside the properly intellectual order, in the order of factors pertaining to the will” (Saint Thomas Aquinas). This need be no stumbling block; by certitude is meant objective evidence and firmness of assent: I am sure of possessing what is true because I see it. Faith is certain, and thus I am sure of possessing what is true; yet I do not see it. Why then am I sure? Because I am united to Someone who sees. Faith is certain, not because it comprises the evidence of a thing seen, but because it is the assent to a Person who sees.
This is just what we would expect. If the essential in faith is not primarily the fragmentary truths, but the Person to whom we tend through these truths—“Him to whose word we assent”—it is quite clear that our certitude will be based on this Person. For it is this Person and he alone, who sees the truths, and who can therefore give our knowledge a solid foundation. As Saint Thomas puts it in an extremely precise formula: The full affirmation does not proceed from the vision of the believer, but from the vision of him in whom one believes. Faith is an assent to the First Truth, that is, to an Infallible Person.
The certitude of faith will consequently be inferior in its evidence to other forms of certitude; but it will be superior to them in “firmness”—that is to say, it will be superior to them in so far as “certitude” implies assuredness in the possession of the truth coupled with fullness of assent.