The End of Ethics, by John Caputo
The moral life is not just concerned with duties, but that which goes beyond the limits of duties. We can strive for the "wholly other," that which is better and more right than we can even conceive of now. Duty calls us out from our selfishness, but then it can also entrap us in our current conceptions. Ethical rules are always provisional, because there is always something we might not have conceived of.
However much Caputo tries to go beyond Kant and Aristotle, I don't believe he does. I think his conception of duty and moderation is different than theirs. He imagines each of these as a joyless following the rules. Though Kant actually believes differently, I see in both of them a joyful striving after excellence. Aristotle's shifting moderation is also the excellence that we can't quite conceive of. Kant's duties, which are abstractions, will never directly translate to singular occurences our moral decisions. So while each abstracted duty might be limited because of its inability to take in all particularities, the categorical imperative -- the ought that would apply universally -- is beyond our conception, because the only person who knows and follows it universally is the holy will, God.
When you reason well, you are free. However, you might discover that your reasoning only leads to one choice. This will happen sometimes in math, for example. You are free to reason, but when you get down to the end of it, you may only find one right answer. The circumstances of morality are not so limited as those of simple math, and so you will never be able to conceive of the perfect moral knowledge, but that doesn't mean it's not out there. But it's beyond our conception. And yet, even if we can't find it, we can reason towards it, and be moving towards the right answer, even if we can't know with holy certainty that we are moving towards the right answer.
So the moral life must allow for that which we have not conceived of yet, that which we have not been able to categorize or place within limits. It must allow for the "wholly other."