Baggett and Walls next consider a more Platonic effort to account for intrinsic human value. Such a view is advanced by those like David Enoch and Erik Wielenberg. They focus on Wielenberg's book, Robust Ethics: The Metaphysics and Epistemology of Godless Normative Realism. Wielenberg's view (known as robust normative realism) is that there are response-independent, non-natural, irreducibly normative truths, objective ones, that when successful in our normative inquiries we discover rather than create or construct. He thinks moral properties supervene on nonmoral properties. Because of issues over supervenience, he distinguishes three types of supervenience.
Let M stand for a moral property. The first variant of supervenience he calls R-supervenience (R for reductive). The way M supervenes on the base properties here is by being reduced to them. Here, M is identical or entirely constituted by the base properties. The second form is A-supervenience (A for Adams). The instantiation of M might be entailed by the instantiation of the base properties together with the instantiation of certain non-base but necessarily instantiated properties. This comes from Robert Adams’ view of finite goodness. His view is that the property of being finitely good is the property of faithfully resembling God's nature. The third variety is called D-supervenience (D for DePaul). M is not identical, or reducible to, or entirely constituted by the base properties, on this view. Rather, the instantiation of the base properties makes (or explains) the instantiation of M. He thinks the most plausible of these is D-supervenience.
He offers a few ways of construing such a making relation. The first is a grounding relation. Morality on this view concerns a sui generis domain (its own unique domain) that can be reduced to, or consist in, facts that might be formulated in other terms. Wielenberg worries that there isn't a well-understood and useful grounding relation that is distinct from other metaphysical relations like identity and constitution.
The second way, which Wielenberg favors, is construing making as causation. He acknowledges various worries. One concern is that causation requires the existence of laws of nature connecting causes and effects, but it seems implausible to suppose there are laws of nature that connect nonmoral and moral properties. Another concern is that causal connections are usually thought to be contingent, but Wielenberg posits a necessary casual connection. Lastly, it is sometimes thought that causes must precede their effects. Wielenberg thinks the answer to these objections is by understanding causation in a particularly robust fashion, the same causal relation many theists take to hold between a state of affairs being divinely willed and the obtaining of that state of affairs. So, when asked why does being an instance of torturing someone just for fun entail moral wrongness, he says it is because being an instance of torturing someone just for fun makes an act wrong. He thinks no further explanation is available (since all explanations must stop somewhere).
Frank Jackson objects that there is always a purely descriptive claim that is necessarily coextensive with an ethical predicate, so there are no sui generis ethical properties. Using his making relation, Wielenberg argues that moral properties have a feature natural properties lack, namely, the former are resultant. Tristram McPherson objects to Wielenberg's account by saying that commitment to brute necessary connections between discontinuous properties counts significantly against a view. Wielenberg admits there is some intuitive force to this objection, but argues that such a principle is self-undermining. Lastly, Wielenberg shows that both theists and his own view are committed to metaphysically necessary brute facts. They come from nowhere and nothing external to them grounds their existence. He thinks ethical facts are such facts.
What about the narrower issue of the intrinsic value of human beings? Wielenberg thinks that his account better explains such value than at least certain theistic explanations. He insists that makes something good must lie entirely within its own nature. It is good in and of itself. He strikes off Mark Murphy's, Adams', Linda Zagzebski's, and Mark Linville's accounts because he thinks that human value is extrinsic on such views. Baggett and Walls will address such concerns in a later chapter.
They now turn their attention to reservations they have about Wielenberg’s account. First, Wielenberg thinks human dignity and worth D-supervene on the property of being human (or some specific features of being human). Baggett and Walls think that such a making relation underdetermines why this causation relation holds. Second, it is question-begging to assume that this supervenience story is consistent with secularism because, if humans are created in the image of God, then being human would have for one of its essential features a relational property of which God is a part. Third, Wielenberg is committed to the causal closure of the physical. This limits him to material and efficient causes, leaving little to no room for formal or final causes. The first person needs to be left out in any final theory. There is no room for mental causation in the context of casual closure. This arguably eliminates the means of treating persons as ends-in-themselves because the attitude of respect for a person presupposes mental causation. Fourth, there is a huge qualitative gap between natural and non-natural, between fact and value, between value and disvalue. Fifth, Wielenberg seems to dismiss the historical relevance of theism to the conviction about intrinsic human value, yet it is not clear that his worldview has the metaphysical resources to ground such truths. Sixth, it is not obvious that his explanatory stopping point is a good one. It is not clear what explanatory work is done by saying that an act of deliberate cruelty simply makes something wrong. He seems to be simply stating a moral fact that is in need of explanation. His explanatory stopping point amounts more to an assertion than argument. So, with these worries, Baggett and Walls do not think that Wielenberg's account sufficiently accounts for intrinsic human dignity and value.