Lewis argues that there has to be a “Mind” behind the Moral Law, because the Law is very much a set of instructions, and only a “Mind”, as opposed to mere matter, can give instructions or commands.
Lewis also talks about the two views about the nature of the universe: the materialist view and the religious view. The materialist thinks that nature is all of reality, while the religious person believes that there is a reality beyond the physical world.
I agree with Lewis. The source of the Moral Law can only be a Mind, because the Moral Law is a set of commands, and only a Mind (or Person) can issue commands. Based on our intuition, the Moral Law is a set of “prescriptions”: We ought to do this, we ought not do that; we should do this, we should not do that, and so on. Only a Mind or Person can prescribe something to someone. Matter cannot do that. Therefore, a Mind must exist as the source of the Moral Law. Who else can this Mind be but God?