CORPUS CHRISTI, TX (Catholic Online) - In this series of "converging and convincing" proofs of God, we founded our proofs on human experience-of desire, of truth, of contingency.  We used the insights of St. Gregory of Nyssa, St. Augustine, and St. Thomas as our guides in developing these proofs.  These sorts of proofs are called a posteriori proofs because they work backwards from experience to God. 

Then we looked at St. Anselm's ontological argument, which moved from thought of God to existence of God.  This proof did not work from experience, but rather from concept to reality, and so it is called an a priori proof. 

Finally, we looked at what might be called introspective proofs--the proof from mysticism, and the proof from an internal assessment of the human condition.  St. John of the Cross and Blaise Pascal were our guides.

Now we turn back to another a posteriori proof.  This one starts from the experience we have of moral duty.  This is the well-nigh universal experience: there are at least some acts that, irrespective of conventional morality, come attached with an ought or an ought not. 

To a certain degree, in a world of rampant relativism, this proof loses some of its force as the conventional relativism (currently, the majority report) seems to poison the well of conscience and of duty.  Yet even in this most relativistic and pluralistic of worlds, there are still some acts that virtually all seem to agree have an ought or an ought not attached to them. 

Rape, adultery, murder, pedophilia, cruelty to animals come with ought nots attached.  Most still think that rearing one's children, taking care of one's parents when they are old, and rendering aid to someone in need have oughts attached to them. 

Some--we may call them the "Flat-earthers" of morality--still maintain that even these ought and ought nots are the result of convention or emotivism, or should be the matter of utilitarian calculation.  But that, to put it mildly, does not seem a very satisfying description of the moral sense.  To put it less mildly, it is plain wrong.

At least at its most basic, the moral sense seems to transcend convention, emotions, and even utility.  In the words of George Eliot, the sense of duty has something "peremptory and absolute" about it.  Those are the words of transcendence.

As Aidan Nichols puts it in his A Grammar of Consent in his understated English way:  "We do not feel happy with the idea that values change be changed at will, although were we purely their creators we could in principle change them quite as legitimately and as often as we change our clothes."  The experience of oughts and ought nots, he says elsewhere more forthrightly, "has an irruptive quality about it: it breaks in on us from without."

The proof of God based upon the felt existence of moral duty can be looked at from two angles. 

First, one can look at this proof beginning from the internal sense of duty and use the illative sense to come to the conclusion that the existence of God is the best explanation for moral duty's existence. 

Second, one can look at this proof by showing that without God, there can be no such thing as morality; in other words, the existence of God is the best support for morality.
 
The oughts and ought nots we acknowledge to exist and which are at the heart of our moral sentiment seem to point to a power outside of us to which we are answerable.  It is difficult-perhaps even impossible-to explain this sense without tracing it back to some transcendent lawgiver: God. 

"On this view," notes Aidan Nichols, "divine transcendence lies at the heart of our moral awareness, grounds our sense of obligation, and justifies that sense before the bar of reason, preventing it from being a mere unintelligibility in experience, a pure surd."

Immanuel Kant recognized the intimate relationship between morals and God.  In fact, because (for complex reasons we won't go into here) he rejected most traditional proofs of God, he found it ...