Natural Law, a/k/a Moral Law. Animals, and atheists, don’t get it.
Atheists get it. They consciously rebel against it.
Humans have spiritual souls and animal souls. Animals have animal souls. Animals will always be animals, but humans have the choice to strive towards their higher, spiritual souls, so they have the ability to sometimes be spiritual and elevate themselves from their basic animal selves. Animals will be animals - that is what they are. So the difference is that Humans have choices, animals do not. In my opinion.