Shafer-Landau's Nontheistic Ethical Nonnaturalism
Russ Shafer-Landau defends Ethical Nonnaturalism, a kind of moral realism that maintains moral facts are real but non-scientific (Shafer-Landau 2013, 54–62). He does so by drawing a close parallel between the methodology in ethics and philosophy in general. Since Ethics is a species of the genus Philosophy, it inherits essential properties of philosophic inquiry, specifically the objective and realistic status of its truths. Therefore, moral realism is true. This parity argument can withstand three objections: the intractability of moral disagreement, the epistemic defeaters posed by such disputes for moral realism, and the causal inefficacy of moral facts.
The first key move establishes the parity argument. Unlike truths derived from a posteriori methods of Science, Metaphysical truths are typically a priori and do not depend upon empirical methods. Doing philosophy is about seeking truths about reality through conceptual and logical analyses. Likewise, foundational moral truths are confirmed not by sensory evidence, but by rigorous philosophical reflection. For example, science can describe that certain acts cause what has been reported as perceived gratuitous suffering, but it cannot normatively judge that such an act is evil and that we are morally obliged to prevent it. Verdicts of this sort are settled by philosophical reasoning, not laboratory findings or sheer induction. Since philosophical truths are objective, moral truths inherit that same status.
The second move deploys this parallel against the problem of the intractability of moral disagreement. The observation that there is no unanimous verdict on moral issues can warrant antirealism about morality. However, deep divides exist throughout the subdomains of philosophy without accepting the antirealist thesis that moral truths grounded independently of agents exist. For example, regardless of the vigorous debate ongoing in philosophy of mind, there either is or is not such a thing as libertarian free will. These disputes do not elicit rejection of realism about the truth of the matter. Proponents from all camps presuppose that there is a mind-independent objective truth they are best attempting to uncover. By the same token, moral disagreement does not necessitate moral antirealism.
The second objection applies the intractability of disagreement to undermine epistemic justification about moral claims. Consider a hypothetical scenario in which I witness my hated nemesis, Smith, die in an unfortunate, fatal accident. The investigators on the scene, upon knowing about my history of animosity with Smith, are justified in suspecting me of foul play. Their incompatible (with my belief), well-justified beliefs do not undermine my own original belief and memory. Second, the principle that mutual rational disagreement always defeats justification is itself subject to intractable rational disagreement and thus self-undermining. Question-begging defenses can even supply positive justification, since anything cited in defense of one's empirical beliefs will seem question-begging to a consistent skeptic, yet we do not conclude that all empirical belief is thereby unjustified.
The third move responds to Harman’s argument from the causal inefficacy of moral facts. The charge holds that realistically construed facts must have independent causal powers; moral facts lack them; therefore, they cannot be construed realistically. The second premise can be conceded, but the first premise must be rejected. Mathematical and epistemic truths (for instance, modus ponens in logic), for example, are causally effete, but they do exist. So do macro-level objects like an organism, distinct from its subatomic constituents. The role of moral facts is not explanatory in the sense of citing causes of events and predicting them. Rather, their role is normative.
Critique
Shafer-Landau offers a solid defense of moral realism against antirealist objections. His response to persistent moral disagreement effectively deflates the hidden false assumption that disagreement is equal to non-existence or non-reality. Likewise, his reply to Harman’s causal test is persuasive, showing that epistemic and logical norms also lack independent causal power. However, the weakest point is his positive metaphysics. Moral facts are declared sui generis, but this avoids rather than answers the grounding question: if moral properties necessarily co-vary with natural ones, what makes them genuinely nonnatural rather than merely epistemically inaccessible to science? The supervenience relation is acknowledged in Section V, but left underdeveloped, and it threatens to reduce moral nonnaturalism to a label rather than a substantive ontological distinction. He does not explicitly mention what natural facts or physical configurations subvene its respective moral fact, for instance, “Love is good,” or “We must quell evil.” By contrast, Christian Ethics, also nonnaturalistic, grounds morality in the good nature and character of the Triune God and provides a clearer and more robust explanation of moral objectivity and normativity.