The Christian tradition is clear on Christian faith being certain, a certainty due to the Holy Spirit, either in revealing the doctrines of faith or in enlightening the believer's mind or both. But as an empirical fact, Christians, even ones with a genuine living faith, do struggle in faith, and at times their belief appears quite uncertain.
If the certainty of faith is defined by a feeling of certainty, the Christians don't have certainty. But that is surely the wrong way to think about. After all, the Christian who has living faith has faith even while asleep (otherwise, no one who died in sleep could be saved!). I suppose that was a cheap shot, since one could define certainty in terms of a disposition to feel certain in appropriate circumstances, but the whole idea of taking a feeling to be central to faith misses the phenomenon of the dark night of faith.
I want to suggest that certainty is tied to ungiveupability. In other words, a belief is the less certain, the more willing we would be to give it up.
One of going from this is to spell this out in terms of commitment. My belief that p is certain to the extent that I am committed to believing p. Now, when I am committed to doing something, I am typically committed to doing it except in exceptional circumstances. And the degree of commmitment can be measured by the amount of exceptional circumstances and their probability—the more exceptions there are and the more likely the exceptions to befall me, the less committed I am. Maximal commitment to A, then, would be commitment to A in all possible circumstances in which one could find oneself.
However, commitment is primarily a normative matter. One can be normatively committed to doing something even if one has no psychological attitude in favor of it. I can be normatively committed to never eating meat while (intentionally) munching on a steak—all it would take would be for me to have just promised never to eat meat. We call this "infidelity to one's commitments", and it is essential to this that the commitment still be binding on one. If commitment is a normative matter of this sort, then the fact that Christians may feel uncertain is beside the point. What matter is that they are committed, i.e., that they are under an obligation (maybe we need to add: that they themselves undertook), not that they feel committed. In other words, the Christian's certainty consists in its being the case that she is obliged to believe, no matter what.
But that can't be the whole story about certainty. The reason is that this story is compatible with unbelief. After all, if one can be unfaithful to one's commitments, and if the certainty of belief were just commitment to believe, then one could have the certainty of belief without belief. And that's absurd. We could add that to have the certainty of belief you need to believe, but the link between the belief and the certainty surely needs to be tighter. Nor will it help to add that the commitment has to be subjectively acknowledged (this subjective acknowledgment of a commitment is sometimes itself called "commitment"). For I can acknowledge an obligation not to eat meat while munching on a steak.
Here is another suggestion. Instead of reading the certainty normatively, read it causally. Here is one take on it. A person x is certain in believing p to the degree that it would be difficult to make her cease to believe p. If, given the present state of the world, it is altogether causally impossible for x to cease to believe p, then we can say that x has absolutely unshakeable certainty that p. Maybe some who believe in the doctrine Reformed folks call "the perseverance of the saints" believe that the elect have this sort of certainty. But this merely causal unshakeability may not be suited to an analysis of certainty, which in the context of the Christian faith seems to have an epistemic component: not only is it that the Christian's faith can't (in some sense to be explained shortly) be shaken, but it is appropriate, epistemically and morally, that it not be shaken. Moreover, I do not think we should commit to "the perseverance of the saints" as understood by the Reformed—there are too many warnings in Scripture about the danger of falling away (though I know the Reformed have their own readings of those). Therefore, we should allow for the possibility that x might freely choose to be irrational and stop believing.
The above remarks fit well with the following account (which I am not actually endorsing as a complete story; I like the thought that this account and my previous normative account should be conjoined):
- x has appropriately unshakeable certainty that p if and only if x believes that p and it is causally necessary that x continue to epistemically obligatorily (or, for what would in practice tend to be a weaker definition: appropriately) believe that p so long as x refrains from gravely immoral actions.
Notice what appropriate unshakeability does not require. First, it does not require that there be a Bayesian credence of one in p. Nor does it require that there be no metaphysically evidence E such that P(p|E) is small. All that's required is that it be causally necessary either that x not observe E or that should x observe E, something should turn up (by the grace of God, immediate or mediate) that would continue to render it epistemically obligatory (or at least permissible) to believe it. The above story is compatible with multiple explanations for the necessity claim. For instance, maybe, the Holy Spirit enlightens the mind in such a way as to internally provide evidence stronger than any that is possible. Or maybe God is committed to ensuring that one will not meet with any strong counter-evidence. Or maybe one has credence 1 and God will help one remain Bayesian-rational and not change that 1.
Whence the causal necessity? I suppose it would be grounded in the promises of God—it is causally impossible that the promises of God not be fulfilled. Or maybe oeconomic necessity would be better here than causal necessity—however, I think oeconomic necessity is a special case of nomic necessity.
I am grateful to Trent Dougherty for a lot of discussions of certainty, out of which this post flows.