Jessica M. Wilson

I argue that an adequate account of non-reductive realization must guarantee satisfaction of a certain condition on the token causal powers associated with (instances of) realized and realizing entities---namely, what I call the 'Subset Condition on Causal Powers' (first introduced in Wilson 1999). In terms of states, the condition requires that the token powers had by a realized state on a given occasion be a proper subset of the token powers had by the state that realizes it on that occasion. Accounts of non-reductive realization conforming to this condition are implementing what I call 'the powers-based subset strategy'. I focus on the crucial case involving mental and brain states; the results may be generalized, as appropriate. I first situate and motivate the strategy by attention to the problem of mental causation; I make the case, in schematic terms, that implementation of the strategy makes room (contra Kim 1989, 1993, 1998, and elsewhere) for mental states to be ontologically and causally autonomous from their realizing physical states, without inducing problematic causal overdetermination, and compatible with both Physicalism and Non-reduction; and I show that several contemporary accounts of non-reductive realization (in terms of functional realization, parthood, and the determinable/determinate relation) are plausibly seen as implementing the strategy. As I also show, implementation of the powers-based strategy does not require endorsement of any particular accounts of either properties or causation---indeed, a categoricalist contingentist Humean can implement the strategy. The schematic location of the strategy in the space of available responses to the problem of mental (more generally, higher-level) causation, as well as the fact that the schema may be metaphysically instantiated, strongly suggests that the strategy is, appropriately generalized and instantiated, sufficient and moreover necessary for non-reductive realization. I go on to defend the sufficiency and necessity claims against a variety of objections, considering, along the way, how the powers-based subset strategy fares against competing accounts of purportedly non-reductive realization in terms of supervenience, token identity, and constitution.

Horgan (1993) proposed that "superdupervenience" - supervenience preserving physicalistic acceptability - is a matter of robust explanation. I argued against him (1999) that (as nearly all physicalist and emergentist accounts reflect) superdupervenience is a matter of Condition on Causal Powers (CCP): every causal power bestowed by the supervenient property is identical with a causal power bestowed by its base property. Here I show that CCP is, as it stands, unsatisfactory,for on the usual understandings of causal power bestowal, it is trivially satisfied or falsified. I offer a revision of CCP which incorporates the evident fact that causal powers are grounded in fundamental forces.

The nonlinearity of a composite system, whereby certain of its features (including powers and behaviors) cannot be seen as linear or other broadly additive combinations of features of the system's composing entities, has been frequently seen as a mark of metaphysical emergence, coupling the dependence of a composite system on an underlying system of composing entities with the composite system's ontological autonomy from its underlying system. But why think that nonlinearity is a mark of emergence, and moreover, of metaphysical rather than merely epistemological emergence? Are there diverse ways in which nonlinearity might enter into an account of properly metaphysical emergence? And what are the prospects for there actually being phenomena that are metaphysically emergent in any available sense? Here I explore the mutual bearing of nonlinearity and metaphysical emergence, with an eye towards answering these and related questions.

Hume argued that experience could not justify commonly held beliefs in singular causal effcacy, according to which individual or singular causes produce their effects or make their effects happen. Hume's discussion has been influential, as motivating the view that Causal reductionism (denying that causal efficacy is an irreducible feature of natural reality) requires Causal generalism (according to which causal relations are metaphysically constituted by patterns of events). Here I argue that causal reductionists---indeed, Hume himself---have previously unappreciated resources for making sense of Causal singularism, associated with a relation that has been curiously underexploited in the causation debates: resemblance. The core idea I explore here is that causation may be metaphysically and epistemologically indicated by the coming-to-be of a resemblance. Comings-to-be of resemblances are epistemically available in the singular instance, even by Hume's strict lights, and, I argue, can justify (albeit fallibly) belief in the holding of singular causal relations; hence Hume's general argument for generalism fails. More to the contemporary metaphysical point, comings-to-be of resemblances provide valuable resources for existing singularist accounts: while neither changes (Ducasse) nor transfers of physical quantities (Fair, Dowe, Salmon) provide a suffciently fine-grained basis for the individuation of causes, either changes or transfers, in combination with comings-to-be of resemblances, can do so.