Here's a link to a recent debate between William Lane Craig and Louise Antony on whether or not God is necessary for morality. It was interesting for me since reading Craig's debates and apologetics works helped get me into philosophy, and Antony was one of my professors when I was an undergraduate at The Ohio State University. Both are moral realists and affirm that there are objective moral truths. I didn't find Craig's arguments that God is necessary for morality to be convincing.
However, here's one of his arguments which has some intuitive appeal and that I'd like to explore. He points out that if God does not exist, then there is no ultimate moral accountability. People will not ultimately get what they deserve, whether this be reward for a life well lived or punishment for horrendous evils. This seems to me to be correct. If naturalism is true, then even if there are objective moral truths, people will not ultimately get what they deserve.
But is there any reason to think the following?
1) If there are objective moral truths, then there will be some ultimate moral accountability.
There is no doubt something less satisfying (at least emotionally) with the naturalistic worldview, but I don't know if I can think of any good reasons to believe that (1) is true. And if (1) is false, there is no problem for the naturalist.
Could we defend (1) just by appealing to intuition? Do most humans have a deep intuition that wrongs must be righted and vice versa? But this intuition is weak at best. I would hope for some more argument. Any suggestions?