Moral arguments take either the existence of morality or some specific feature of morality to imply the existence of God. It is only if God exists, the moral argument suggests, that the moral facts could be as they are, or even that there could be any moral facts at all. There are several different forms of moral argument. Here, three are considered.

The first is a formal moral argument, taking the normativity and authority of morality to entail that it is has a divine origin.

The second is a perfectionist moral argument, suggesting that it is only by postulating the existence of God that we can make sense of the high standards that morality requires of us.

The third is Kant’s moral argument, which begins with the thought that we have good reason to behave morally and concludes that this can only be the case if there is a God that administers justice in the afterlife.

The Formal Moral Argument

The formal moral argument takes the form of morality to imply that it has a divine origin. Morality is prescriptive, it tells us what to do; this, the moral argument suggests, entails that it is prescribed by someone. Morality is also ultimately authoritative, its authority is greater than any human institution; this, the argument suggests, entails that it was not prescribed by any human institution, but must rather have a supernatural source.

The Perfectionist Moral Argument

The perfectionist moral argument begins by setting up a problem. There are three apparent truths about morality that are mutually inconsistent: we ought to be perfect; ought implies can; we cannot be perfect. How are we to resolve this contradiction?

The perfectionist moral argument suggests that the most plausible resolution of the conflict is not to deny our duty by saying that it’s okay to fall short of the moral standard, or to exaggerate our potential for moral behaviour by saying that we can meet that standard really, but to invoke God. If God exists, the argument suggests, then he can help us to bridge the gap between what we are able to do by our own strength and what morality requires of us.

The Kantian Moral Argument

Kant’s moral argument begins with the thought that moral behaviour is rational, that we have good reason to behave morally. This, it suggests, can only be the case if it is ultimately in our interests to behave rationally. If immoral behaviour leads to the best consequences then it immoral rather than moral behaviour that is rational. Looking around the world, thuogh, we see that in many cases immoral behaviour does profit more than moral behaviour, that life isn‘t fair. Moral behaviour, then, will only be rational is there is more than this life, if justice is administered in the next life. The fundamental thought that morality is a rational enterprise thus entails something like the Christian view of the afterlife.