Kierkegaard somewhere says that the best argument for the Gospel is something like this: Everyone agrees that the moral teaching of the Gospel—love of neighbor and so on—is morally good. Thus, one should wholeheartedly strive to live it. And one will find oneself unable to do so, which will lead to one's throwing oneself on the grace of God.
Abstracting from the details, Kierkegaard is committed to something like this thesis:
- A sufficiently wholehearted attempt to live the morally upright life puts one in a position to have an epistemically justified faith.
But if one fails to make that wholehearted effort, then one cannot reasonably complain about hiddenness. This story may seem offensive to non-Christians, but I suspect that Kierkegaard also thinks very few Christians make that wholehearted attempt.