Online research in philosophy

Non-reductive moral realism is the view that there are moral properties which cannot be reduced to natural properties. If moral properties exist, it is plausible that they strongly supervene on non-moral properties- more specifically, on mental, social, and biological properties. There may also be good reasons for thinking that moral properties are irreducible. However, strong supervenience and irreducibility seem incompatible. Strong supervenience entails that there is an enormous number of modal truths (specifically, truths about exactly which non-moral properties necessitate which moral properties); and all these modal truths must be explained. If these modal truths can all be explained, then it must be a fundamental truth about the essence of each moral property that the moral property is necessarily equivalent to some property that can be specified purely in mental, social and biological terms; and this fundamental truth appears to be a reduction of the moral property in question. The best way to resist this argument is by resorting to the claim that mental and social properties are not, strictly speaking, natural properties, but are instead properties that can only be analysed in partly normative terms. Acceptance of that claim is the price of non-reductive moral realism.

“Supervenience”, though a philosophers’ notion, has a venerable history. It was used by Leibniz to say that relations are nothing over and above the intrinsic properties of their relata, by Sidgwick to say that moral characteristics covary with non-moral ones, by Moore to say that the former are grounded in the latter, by Hare to say that they stand in some relation of strict implication and by Davidson (1970: 214) to say that “mental characteristics are in some sense dependent, or supervenient, on physical characteristics” (cf. Kim 1990: 136–138). Here is what Robert Stal- naker (1996) says about the “intuitive ideas that motivate the attempts to articulate concepts of supervenience”:

To say that the A-properties or facts are supervenient on the B-properties or facts is
to say that the A-facts are, in a sense, redundant, since they are already implicitly
specified when one has specified all the B-facts. A-facts are not fact ‘over and above’
the B-facts, not something ‘separate’. To state an A-fact, or ascribe an A-property, is
to describe the same reality in a different way, at a different level of abstraction, by
carving the same world at different joints. (Stalnaker 1996: 87)

Kim (1990: 140) identifies three key features of our concept of supervenience: covariance, depend- ency and nonreducibility (where “non-reducibility” means that the supervenience of A-features on B-features is consistent with the former not being reducible to the latter).¹ Explanation, sometimes required for reducibility, is absent : supervenience claims state that some patterns of property covariation hold, without explaining why they hold.².

In his recent book, Jaegwon Kim argues thatpsychophysical supervenience withoutpsychophysical reduction renders mentalcausation `unintelligible'. He also claimsthat, contrary to popular opinion, his argumentagainst supervenient mental causation cannot begeneralized so as to threaten the causalefficacy of other `higher-level' properties:e.g., the properties of special sciences likebiology. In this paper, I argue that none ofthe considerations Kim advances are sufficientto keep the supervenience argument fromgeneralizing to all higher-level properties,and that Kim's position in fact entails thatonly the properties of fundamental physicalparticles are causally efficacious.

Horgan claims that physicalism requires "superdupervenience" -- supervenience plus robust ontological explanation of the supervenient in terms of the base properties. I argue that Horgan's account fails to rule out physically unacceptable emergence. I rather suggest (in the earliest explicit presentation of the powers-based subset strategy) that this and other unacceptable possibilities may be ruled out by requiring that each individual causal power in the set associated with a given supervenient property be numerically identical with a causal power in the set associated with its base property. Satisfying this condition is all that is needed to render supervenience superduper. I go on to show that a wide variety of physicalist accounts, both reductive and non-reductive, are implicitly or explicitly designed to meet this condition, and so are more similar than they seem.

The discussion of supervenience is replete with the use of in?nitary logical operations. For instance, one may often ?nd a supervenient property that corresponds to an in?nite collection of supervenience-base properties, and then ask about the in?nite disjunction of all those base properties. This is crucial to a well-known argument of Kim (1984) that supervenience comes nearer to reduction than many non-reductive physicalists suppose. It also appears in recent discussions such as Jackson (1998).

I show how existing concepts of supervenience relate to two more fundamental ontological relations: determination and dependence. Determination says that the supervenient properties of a thing are a function of its base properties, while dependence says that having a supervenient property implies having a base property. I show that most varieties of supervenience are either determination relations or determination relations conjoined with dependence relations. In the process of unpacking these connections I identify limitations of existing concepts of supervenience and provide ways of overcoming them. What results is a more precise, flexible, and powerful set of tools for relating sets of properties than current concepts of supervenience provide. I apply these tools to a recalcitrant problem in the physicalism literature – the problem of extras.

One of several problems concerning the possibility of mental causation is that the causal potential of a supervenient property seems to be absorbed by its supervenience base if that base and the supervenient property are not identical. If the causal powers of the supervenient property are a proper subset of the causal powers of the supervenience base then, according to the causal individuation of properties, the supervenience base seems to do all the causal work and the supervenient property appears to be futile. Against this consequence it is possible to argue, first, that the relevant properties of causes must be in some sense proportional to the relevant properties of their effects and, second, that the principle of causal closure serving as a premise in the supervenience argument is probably false. The constraint that the relevant properties of causes should be proportional to the relevant properties of their effects together with the falsity of the closure principle leads to a restoration of the causal efficacy of supervenient properties.