Reading through Vanhoozer’s Drama of Doctrine a couple of years ago, I made a mental note of his discussion on certainty in the Christian faith. I loved the book, but was wrestling over his critique of absolute or apodictic certainty in the faith. After all, aren’t we certain that God exists and that our sins are forgiven in Christ?
Concerning certainty, the Reformed scholastics have much to say, especially in the light of Descartes’ “clear and distinct” standard of truth. For example, Turretin notes that there are three species of certainty 1) mathematical, 2) moral, and 3) theological (Institutes, II.iv.22).
Mathematical certainty (a.k.a. metaphysical certainty) has to do with things known by nature and things demonstrated by nature. For example, 1 + 1 = 2. This is metaphysically or mathematically certain: you can see and prove it and it is known by nature.
Moral certainty has to do with truth that cannot be demonstrated, but are so clear that all sensible men agree upon them. For example, we know that Abraham Lincoln was the president of the U.S. during the Civil War.
Theological certainty has to do with the truths that cannot be demonstrated or known by nature or empirical evidence, but truths that are founded on things divine – i.e. revelation. Scripture is this revelation, and it does not belong to the mathematically certain category, else faith would not be required. Neither does Scripture belong to the moral certainty category, else our faith would simply be historical assent, much like our assent to the fact that Lincoln was the president during the Civil War. We are theologically certain, however, that God is God and that Jesus died to save his people from their sins. Saving faith carries with it a “certain certainty.”
R. Muller describes the Reformed scholastic teaching of certainty this way: “Since God is neither a natural principle nor a thing that can be known immediately through itself, but rather is known through his self-revelation, theology has its own species of certainty, related to the way of knowing that is specific to theology: faith. This definition, although not at all polemically stated, does have a gently anti-Cartesian edge in its denial of mathematical certainty” (PRRD, I.412).
Of course, this has everything to do with our finiteness, sinfulness, ectypal and analogical knowledge, and our “pilgrim” theology. We are not gods, nor do we have God-like archetypal and univocal certainty. Yet what we have is sufficient – theological certainty, or certainty of faith that “God is” and that the gospel is true for us.
This is helpful for our own wrestlings in the Christian life; it chases sinful doubts, and it frees us up from trying to attain mathematical certainty for things divine. It is also quite helpful for apologetic purposes, as we can show skeptics who want “proof” that they are pressing Christianity into wrong categories – categories that they themselves keep distinct in their daily lives.