St. John is the patron saint of epistemology. That is, he is patron saint of a biblical approach to believing and knowing. He is not the patron saint of unbelieving epistemology. How do we know? How do we know that we know? These are reasonable questions to ask at the foot of the cross — and nowhere else.
We believe so that we may know. We must believe the truth, however, and not believe a lie. We are utterly dependent upon the grace of God in this. We cannot save ourselves; we cannot protect ourselves; we cannot know ourselves. Unless we know God, we cannot understand ourselves or our knowing. And if we come to know God, it is by means of His sheer gift, and then we have the mind of Christ. When this happens, all things come into focus.
The serpent, subtle as ever, wants to push back behind this faith, and wants us to inquire into the “philosophical preconditions” for believing. He needs to put his epistemology of unbelief somewhere. The epistemology of unbelief says that it wants to understand in order that it might believe. This is theologically incoherent, but more importantly, it is a lie. What it actually means that that a man “wants to understand, so he can gum up the argumentation of understanding, so that he doesn’t have to believe.” To this, St. John calls us to believe in Jesus, the Light that has come into the world. And in this believing, we will come to know. When this is stated, all the philosophy departments set up the baying of their hounds, “Fideism!” — which is quite a mouthful for a hound. But those who believe know that fideism is just another form of unbelief. And how do they know? They have believed in Jesus Christ.