In a recent post, PZ Myers complains that a couple of atheists botched their response to ‘the’ moral argument for God’s existence. He writes:
There is a common line of attack Christians use in debates with atheists, and I genuinely detest it. It’s to ask the question, “where do your morals come from?” I detest it because it is not a sincere question at all — they don’t care about your answer, they’re just trying to get you to say that you do not accept the authority of a deity, so that they can then declare that you are an evil person because you do not derive your morals from the same source they do, and therefore you are amoral. It is, of course, false to declare that someone with a different morality than yours is amoral, but that doesn’t stop those sleazebags.
Even if Myers were right that the question is insincere, that still doesn’t refute the argument. With all due respect to Myers, I detest, in any context, the presumptuousness of assuming that one person is inside another person’s mind and knows their thoughts, feelings, and motives. I think he is flat out wrong about the sincerity of the question; I think many people do have genuine questions about the foundations of morality.
Other than (perhaps?) the question, “Where do your morals come from?”, Myers doesn’t quote anything the Christian debaters actually said, so I don’t know which argument the Christian debaters used. Myers put the words “objective morality” in the title of his post, however, so I’m going to assume that the Christians used an argument similar to William Lane Craig’s version of the moral argument. If that assumption is wrong, Myers can correct me.
Myers summarizes his “objective humanist morality” as based upon interest, consent, harm, and stigma. Unfortunately Myers seems to have mixed up normative ethics, which is concerned with what we ought or ought not to do, with metaethics, which, among other things, is concerned with the ontological foundation of moral properties (like moral obligations and moral values). Even if his normative principles of interest, consent, harm, and stigma are perfectly correct, Myers still has said nothing about what makes his principles objective. At best, his calling morality an “objective humanist morality” simply summarizes the conclusion of an argument he hasn’t (yet) provided: Myers has given no argument which shows that objective morality can exist without God.
To say that morality is objective is to say that it doesn’t depend upon the subjective states of a person like feelings, beliefs, emotions, thoughts, etc. So when someone says, “Moral principle X is true,” we can ask, “What makes X true?” Take, for example, harm. Myers writes:
I avoid behaviors that cause harm to others.
Again, this is not done because an authority told me to do no harm, but is derived from self-interest and empathy. I do not want to be harmed, so I should not harm others. And because I, like most human beings, have empathy, seeing harm done to others causes me genuine distress.
So here we have a (normative) moral principle: we should avoid behaviors that cause harm to others. What makes that true? According to Myers, the answer is “self-interest and empathy.” This simply pushes the problem back a step. What makes moral principles “derived from self-interest and empathy” true? If the answer is, “That’s what humans have decided,” then that’s not an objective morality, by definition. Nor is the question asking, “Why should I be moral?” That’s a different subject.
Update: 8-May-12 5:15PM
I just identified the Christian debate opponents for the debate witnessed by Myers: Paul Chamberlain and Michael Horner. Horner’s account of the debate is available online. Based upon my familiarity with Horner’s arguments, I am now even more confident that the moral argument used by Chamberlain and Horner was essentially the same as the version used by William Lane Craig in his debates.
 I’ve put ‘the’ in scare quotes because there are many distinct types of moral arguments for God’s existence, so it’s misleading to suggest there is only one. This is not to suggest that PZ Meyers makes this mistake, however.