The Moral Law argument is a long standing rational proof of the existence of God, made famous by Kant and more recently William Lane Craig.
The Moral Law argument is based on the premise that humans know “right” from “wrong”. The process of knowing right from wrong, we call Morality. The fact all sane humans know this, means that knowing “right” from “wrong” is objective within humanity, therefore we refer to it as Objective Moral Values.
The existence of such objective morality is at least suggestive of some higher authority, as there needs to be a source for these aspirations, its is not possible for there to exist a command, without there being a commander, just like there can’t be something that is being carried unless there is something else that is carrying it. There can’t be something that is popular unless there are lots of people that like it. So to summarise, if moral facts are a command, what is the source of this command?
Morality is of over-riding importance, it implies a universal system of justice and reward. If someone morally ought to do something, then this supersedes any other considerations. It might be in an individual’s best interest not to give any money to charity, but morally they should do, so most do, even though it actually makes them poorer, and it has no tangible benefit to them at all. It might be in one’s best interest to pretend that there too busy to see relatives, but morally they ought not to, so all things considered they ought not to, and they should go and see their family. If someone has one reason to do one thing, but morally ought to do another thing, then all things considered they ought to do the other thing. Morality over-rules everything. Morality has ultimate authority. Commands, though, are only as authoritative as the person that commands them.
As morality has more authority than any individual or institution, the moral argument suggests, morality can not have been commanded by any human person or institution. As morality has ultimate authority, as morality over-rules everything, morality must have been commanded by someone who has authority over everything. The existence of morality thus points us to a being that is greater than any of us and that rules over all creation. Therefore the source of morality must be the creator of the universe, the ultimate being in authority, God.
Kant remarked that because there are Objective Moral Values, there must be a God and afterlife, his rationale is as follows:
- Moral behavior is rational behavior, and therefore it is quite reasonable on our part to respect morality in our lives. If one ought to do something, one has a reason to do it. For instance, a person who knows that he ought to give money to charity has good reason to give money to charity. Moral behavior, Kant said, is always rational.
- The rational nature of moral behavior depends on the guarantee that it would be rewarded. But we see that sinful actions often bring profits rather than moral actions, and so sinful actions would become rational considering the profits, of course on the condition that sinful actions bring no comebacks. It is only if sinful actions will surely be punished in the end, we have reason to avoid sinful actions and prefer moral actions. In other words, moral behavior will be rational only if justice is done ultimately by the incurring of due punishments for sinful actions.
- We have no guarantee that justice will be done in this world. For in this world we find good people suffering and bad people flourishing, for life here and now is not fair.
If you are interested in the evidence of the existence of God, then I suggest you consider the book I have written on the topic which goes into much more detail and covers many other arguments both for and against.