The argument from unbelief takes the existence of unbelievers as evidence against Christian theism. If Christianity is true, according to this argument, then God knows how to, wants to, and is able to convince everyone of his existence. Christianity is thus seen to conflict with divine hiddenness. That God remains hidden from many of us, that he has not taken the steps necessary to cause all to believe in him, seems to be evidence against Christianity.

A natural response to this argument appeals to the importance of faith, and to the necessity of uncertainty for faith. Faith is traditionally seen by Christianity as a virtue. Arguably, though faith is only possible if the evidence for God’s existence leaves room for doubt. God’s hiddenness is thus explained as a necessary means of bringing about a great good, faith.

There are several different ways of understanding the relationship between faith and reason, but on the traditional Thomist conception of faith, irresistible evidence makes faith impossible. This is because, on this view, one of the conditions that a belief must satisfy if it is to constitute faith is that it must be voluntary; faith can only result when we choose to believe. If our evidence is utterly convincing, though, irresistible, then choice is impossible; we are compelled to believe. Given utterly convincing evidence for God’s existence, then, faith would be impossible.

This gives the theist a way of answering the argument from unbelief. Faith is a virtue, but is only possible if the evidence for God’s existence is imperfect, resistible. God therefore has reason to give us only imperfect evidence of his existence, to remain at least partially hidden from us. If our evidence for God’s existence is resistible, though, then it is possible, even likely, that some will resist it, that there will be unbelievers. Even if God exists and is as Christainity portrays him, then, we would expect there to be some unbelievers.

There are several difficulties with this response to the argument from unbelief. The Thomist conception of faith is contentious, as it rests on the idea that belief is voluntary, which many doubt. Many philosophers think that we cannot choose what to believe at all, and so that faith of the kind that Aquinas describes is impossible. It is also unclear why it is that faith, on the Thomist conception, is such a good thing. Is it not better to know something for certain than it is to speculate on uncertain evidence? Would it not be better, then, if God did away with faith and gave us all knowledge of his existence by revealing himself fully.