In an exchange at Slate with Will Saletan, Ross Douthat writes:

[T]he more purely secular liberalism has become, the more it has spent down its Christian inheritance—the more its ideals seem to hang from what Christopher Hitchens’ Calvinist sparring partner Douglas Wilson has called intellectual “skyhooks,” suspended halfway between our earth and the heaven on which many liberals have long since given up. Say what you will about the prosperity gospel and the cult of the God Within and the other theologies I criticize in Bad Religion, but at least they have a metaphysically coherent picture of the universe to justify their claims. Whereas much of today’s liberalism expects me to respect its moral fervor even as it denies the revelation that once justified that fervor in the first place. It insists that it is a purely secular and scientific enterprise even as it grounds its politics in metaphysical claims. (You will not find the principle of absolute human equality in evolutionary theory, or universal human rights anywhere in physics.) It complains that Christian teachings on homosexuality do violence to gay people’s equal dignity—but if the world is just matter in motion, whence comes this dignity? What justifies and sustains it? Why should I grant it such intense, almost supernatural respect?

Now, I know Ross has read his Euthyphro, but since he talks here as though he hasn’t, I’ll go ahead and make the obvious point: Invoking God doesn’t actually get you very far in ethics, because ascribing “goodness” to a deity or its laws is meaningless unless there’s some independent criterion for this. At best, God gets you two things: First, a plausible prudential internal motivation to behave “morally” (because God will punish you if you don’t), though of the same formal sort as the motivation you might have to obey a powerful state or a whimsical alien overlord. Second, a potential form of “expert validation” for independent moral truths we lack direct epistemic access to, as when we accept certain propositions on the grounds that mathematicians or scientists have confirmed them, even if most of us are incapable of comprehending the detailed proof. But invoking God doesn’t solve any of the problems that secular moral philosophers grapple with—it’s essentially just a way of gesturing at a black box, wherein we’re assured the answer lies, and asserting that we needn’t worry our pretty little heads about it.

If divine commandments are not supposed to be mere arbitrary rules we obey out of fear, then every question Ross thinks confronts the secular moralist reappears within a theistic framework. Why does being made in the image of God, whatever that entails, imbue people with dignity? Why would it obligate us to treat them (or refrain from treating them) in certain ways? Why should we believe that supernatural properties can supply us with the appropriate sort of reasons if natural properties cannot? As with cosmological questions, appealing to God defers the questions rather than answering them. In the moral case, one might add, it seems to do so in a rather unattractive way: It turns out that the reasons we have to respect other persons are rather like the reasons we have to respect property—flowing not from anything intrinsic to the object, but from the consideration due some third party who is the real source of value.

One way to highlight what’s wrong with this picture is by reflecting on the familiar but confused idea implicit in the observation: “You will not find the principle of absolute human equality in evolutionary theory, or universal human rights anywhere in physics.” Nor an account of plate tectonics in calculus, a diagnosis of schizophrenia in game theory, or the concept of Turing completeness in astronomy. It is not some kind of contingent disappointment that physics and biology have not discovered dutyons mixed in somewhere with the bosons and protons, or failed to detect the Rights Field generated by the human body: The kinds of facts studied by the natural sciences are, more or less by definition, not normative facts. But the same goes for supernatural facts. If there is a God, we still need ethics to get us across the gap to ought. Facts about the divine, if we had any, would just join natural facts in the pool of data for secular moral philosophy. [Addendum: This graf is not meant to take a position on the more contentious question of whether any natural facts—including facts about mental states—could be normative facts.]

Ross is certainly correct that we owe a debt to thinkers in the Christian tradition—who in turn owe one to pagan thinkers of ancient Greece and Rome—but it’s far less clear that the value of their contributions rests crucially on their theistic metaphysical trappings. Aquinas thought that moral law could be derived by human reason from reflection on natural facts. John Locke may have peppered his political philosophy with a generous dose of theology, but it’s not at all obvious that what was always most interesting and compelling in his arguments requires supernatural support. For that matter, Newton was famously quite devout, and thought the physical laws he described ordained by God. But it turns out that F=MA even after you reject that premise: Physical law (like moral law?) does not require a lawgiver. None of which is to deny there’s plenty of hard problems left for modern moral philosophers to solve, but they’re mostly problems that were obscured rather than seriously addressed by theology.

Ross closes with a pitch to modern liberals who wish to preserve ideals like human rights, suggesting that “for all its strange claims and confounding commandments, [Christianity] might still provide a better home for humankind than whatever destination our civilization is headed for.” This gets us to the odd circularity that’s always at the heart of moralized defenses of religion. The notion seems to be that someone not (yet) convinced of Christian doctrine would have strong reasons—strong humanistic reasons—to hope for a world in which human dignity and individual rights are respected. But then why aren’t these reasons enough to do the job on their own? If Christian doctrine is true, then external considerations are irrelevant to the truth of whatever normative beliefs it supports. If it is false, and our moral beliefs are unsustainable without this false premise, then we should be glad to be rid of false and unjustifiable beliefs. If we think it would be awful to discard those beliefs, then that awfulness is sufficient reason to hang onto them without any religious scaffolding. The only coherent version of this argument is that people who don’t think about it very hard will more readily believe that the religious version of this story provides reasons to respect rights, and comport themselves accordingly. If that were true, it might lead us to hope most people continue to hold the relevant false beliefs, but such pessimism seems premature.