One form of takes the fact that there is a gap between our moral duties and what we are capable of doing to imply the existence of God. This argument makes use of a Kantian ethical framework, but it is not quite the moral argument proposed by Kant; an excellent exposition of an argument of this type can be found in John E Hare’s The Moral Gap.

The argument’s structure is roughly as follows:

The Perfectionist Moral Argument

(1) We ought to be morally perfect.
(2) If we ought to be morally perfect, then we can be morally perfect.
(3) We cannot be morally perfect unless God exists.
Therefore:
(4) God exists.

Perfectionist Morality

Morality places great demands upon us. It does not require that we do our duty some of the time, or most of the time; rather, it requires that we always and unfailingly fulfil our duty in every detail. Morality is perfectionist. Coming close to doing as we ought, though it may be better than falling short by a long way, isn‘t good enough; we should do better.

The Inevitability of Imperfection

This perfectionist moral standard is one that we all miss. As the Bible puts it in Romans 3:10, “there is none that is righteous, not even one”. Indeed, it’s a standard that we are all bound to miss. We cannot fulfil every one of our obligations; we are certain to break the moral law sooner or later.

The Impossibility of Moral Restoration

Once we break the moral law, falling short of its standard, there is nothing that we can do to restore ourselves to righteousness. Fulfilling our duty in every detail from that moment forth will not do so, but will only prevent us from falling further. Exceeding our duty, which might be perhaps restore us, is not possible; just as one cannot score more than 100% on an exam, one cannot exceed a standard that requires perfection.

We are, then, forlorn. We have a duty to be perfect, will inevitably fall from moral perfection, and once fallen cannot restore ourselves to perfection. It seems that we cannot win.

The Moral Puzzle

This puts us in a situation that many philosophers judge to be impossible. A fundamental principle of morality, stressed particularly by , is that “ought” implies “can”; if we have an obligation to do a thing then it logically follows that we are able to do it. According to this principle, morality cannot require of us more than we are able to give. If we cannot be perfect, then we cannot have a duty to be perfect; if we have a duty to be perfect, then it must be possible for us to do so.

There are three apparent truths, then, that are mutually inconsistent: we ought to be morally perfect; if we ought to be morally perfect then we can be morally perfect; we cannot be morally perfect. How are we to make sense of this? How are we to resolve the tension between them?

Solutions to the Problem

One response is to drop the moral perfectionism, to try to resolve the contradiction by saying that it is sometimes okay to break the moral law. In practice, this is how many people think: those of us that consider ourselves to be ‘good people‘ don‘t deny that we occasionally do bad things; of course we occasionally do bad things, we just don‘t do them often enough to count as bad people. This doesn‘t seem right though; how can it ever be morally okay to break the moral law?

There is another way to resolve the contradition, the solution proposed by the perfectionist moral argument. The tension between the three apparent truths can be resolved by invoking God’s assistance and maintaining that moral perfection can be attained. According to this view, we cannot achieve moral perfection by our own strength, but we can do so with God’s help, which is available to us. God can forgive us; God can take the punishment for our sins; God can restore us to righteousness.

It is, then, possible for us to fulfil our duty to be perfect, but only if God exists. That we have a duty to be perfect, which entails that it is possible for us to be perfect, therefore entails that God exists.