So what can the atheist do with premise (1): "If God does not exist, then objective moral values do not exist"?
Last time I mentioned that in order to refute (1), the atheist must either deny that objective moral values exist (which we discussed), or else admit their existence but attempt to explain them apart from God. This is in fact the line taken by most non-theistic philosophers at this point (which is testimony itself of the inadequacy of relativism).
So how can objective moral values exist if God doesn't? I said that we'd examine the best of their attempts to answer this question. Well here it is. Are you ready?
They just do.
I'm not kidding.
Once they've admitted that moral values are objective (i.e. independent of human perception)--which most will readily do at this point--if you push them to explain the existence of these values, the best atheist philosophers in the world will literally just assert them with no justification.
Now, to be fair, they'll likely spice it up a bit. They'll use fancy words like 'necessary supervenience of moral properties on natural states' or some such language. But at the end of the day, it boils down to positing objective moral truths as brute fact, without explanation.
One attempt even asserts that maybe objective moral values literally exist as necessary metaphysical entities. If you know Plato, this should sound familiar because it's basically a handy modern version of his Theory of Forms. The problem is, nobody buys that. What does it even mean? How would the value 'Compassion' just exist? And even if it did, how could we relate to it? Further still, how could we get moral obligation from such a concept?
Is it just me or is it painfully obvious what's going on here? Some of the best ethicists in the world are willing to suspend otherwise sound judgment and assent to the explanation "That's just the way it is." And this from some of the same people who would criticize Christians for responding to problems this way.
Why do this? Could it be to avoid a conclusion with consequences?
I'll let you decide.