Jessica M. Wilson

Arguably no concept is more fundamental to science than that of causality, for investigations into cases of existence, persistence, and change in the natural world are largely investigations into the causes of these phenomena. Yet the metaphysics and epistemology of causality remain unclear. For example, the ontological categories of the causal relata have been taken to be objects (Hume 1739), events (Davidson 1967), properties (Armstrong 1978), processes (Salmon 1984), variables (Hitchcock 1993), and facts (Mellor 1995). (For convenience, causes and effects will usually be understood as events in what follows.) Complicating matters, causal relations may be singular (Socrates’s drinking hemlock caused Socrates’s death) or general (Drinking hemlock causes death); hence the relata might be tokens (e.g., instances of properties) or types (e.g., types of events) of the category in question. Other questions up for grabs are: Are singular causes metaphysically and/or epistemologically prior to general causes or vice versa (or neither)? What grounds the intuitive asymmetry of the causal relation? Are macro-causal relations reducible to micro-causal relations? And perhaps most importantly: Are causal facts (e.g., the holding of causal relations) reducible to non-causal facts (e.g., the holding of certain spatiotemporal relations)?

Why believe Hume's Dictum, according to which there are, roughly speaking, no necessary connections between wholly distinct entities? Schaffer suggests that HD, at least as applied to causal or nomological connections, is motivated as required by the best account of of counterfactuals---namely, a similarity-based possible worlds account, where the operative notion of similarity requires 'miracles'---more specifically, worlds where entities of the same type that actually exist enter into different laws. The main cited motivations for such an account of similarity are first, that some salient contexts presuppose CF asymmetry, and second, that accounts of CFs failing to presuppose CF asymmetry are epistemologically problematic, such that under conditions of determinism, the variations in initial micro-conditions needed to implement a given counterfactual antecedent would result in so many changes to macro-states that evaluation of CFs would be rendered practically impossible. Against the first reason, I argue that no non-artificial contexts presuppose CF asymmetry; against the second, I observe that such micro-variation is compatible, in principle, with significant similarity as regards macroscopic states of affairs---enough, in particular, to allow CFs to be appropriately evaluated

In Meaning and Necessity (1947/1950), Carnap advances an intensional semantic framework on which modal claims are true in virtue of semantical rules alone, and so are a priori. In 'Empiricism, Semantics, and Ontology' (1950), Carnap advances an epistemic-ontological framework on which metaphysical claims are either trivial or meaningless, since lacking any means of substantive confirmation. Carnap carried out these projects two decades before Kripke influentially argued, in Naming and Necessity (1972/1980), that some modal claims are true a posteriori. How should a neo-Carnapian respond to Kripke's results? Some (notably, Chalmers and Jackson, in their 2001) have suggested that an extension of intensional semantics along lines of "epistemic two-dimensionalism" can accommodate Kripke's results while largely preserving commitment to the semantics-based a priority of modal claims. Here we consider how best to implement this suggestion, and how the resulting semantics fits with Carnap's second project. We find that the most promising (and most Carnapian!) post-Kripke version of Carnap’s semantics---abductive two-dimensionalism---presupposes an epistemology which undermines Carnap's metaphysical anti-realism.

Physicalism is the thesis that all entities are nothing over and above physical entities. Here I investigate into whether and how physicalism might be formulated so as to substantively contrast with its best traditional rivals---including and especially emergentism. Formulating physicalism requires making sense of both the physical/non-physical distinction and the nothing/something over and above distinction. It has been argued that no distinction between the physical and the non-physical exists, that can serve as the basis for a sub stantive physicalism. But such arguments miss the mark, for participants to the physicalism debates do not disagree about the boundary of the physical, which, while roughly drawn is clear enough for debate to proceed. Rather, participants disagree on whether there are any entities over and above those entities they agree are physical. Hence the viability of physicalism primarily depends on the over and above distinction. ;I argue that existing accounts of over and aboveness are inadequate, for the key class of cases where two properties are instanced in a single subject, and one property is supposed to necessitate the other, with at least nomological necessity. I go on to provide an adequate account of over and aboveness, by reference to the notion of a fundamental force . We can formulate physicalism and emergentism using Force-relative Over and Aboveness: according to physicalism, all causal powers bestowed by all properties are grounded only in fundamental physical forces; according to emergentism, some causal powers are grounded in a new fundamental force, different from any physical force. ;Understanding over and aboveness as involving fundamental forces is not new. But arguments against forces have lately been accepted; hence the notable absence of forces from contemporary philosophizing. I distinguish two uses of 'force', and show that these arguments do not tell against fundamental forces. I then give positive arguments for admitting fundamental forces, stemming from the reasonable hypothesis that fundamental forces are collections of interacting fields. Forces, so understood, are ontologically defensible; and thus can serve as the needed basis for formulating physicalism and emergentism

Humeans and non-Humeans reasonably agree that there may be necessary connections between entities that are identical or merely partly distinct—between, e.g., sets and their individual members, fusions and their individual parts, instances of determinates and determinables, members of certain natural kinds and certain of their intrinsic properties, and (especially among physicalists) certain physical and mental states. Humeans maintain, however, that as per “Hume’s Dictum”, there are no necessary connections between entities that are wholly distinct;1 and in particular, no necessary causal connections between such entities (even when the background conditions requisite for causation are in place). The Humean’s differential treatment appears principled, in reflecting that commonly accepted necessary connections involve constitutional relations, whereas wholly distinct entities (notably, causes and effects) do not constitute each other. I’ll argue, however, that the appearance of principle is not genuine, as per the following conditional: Constitutional→Causal: If one accepts certain constitutional necessities, one should accept certain causal necessities. This result provides needed leverage in assessing the two main frameworks in the metaphysics of science, treating natural kinds, causes, laws of nature, and the like. These frameworks differ primarily on whether Hume’s Dictum is taken as a working constraint on theorizing; and it has proved difficult for either side to criticize the other without presupposing their preferred stance on the dictum, hence talking past one another. The arguments for Constitutional→Causal are based, however, in general and independent considerations about what facts in the world might plausibly warrant our beliefs in certain constitutional necessities involving broadly scientific entities. The Humean can respond to these arguments, which reveal a deep tension in their view, at attendant costs of implausibilty and adhocery. The non-Humean framework doesn’t face any such tension between constitutional and causal necessities, however, and so in this respect comes out ahead.

In what does philosophical progress consist? 'Vertical' progress corresponds to development within a specific paradigm/framework for theorizing (of the sort associated, revolutions aside, with science); 'horizontal' progress corresponds to the identification and cultivation of diverse paradigms (of the sort associated, conservativism aside, with art and pure mathematics). Philosophical progress seems to involve both horizontal and vertical dimensions, in a way that is somewhat puzzling: philosophers work in a number of competing frameworks (like artists or mathematicians), while typically maintaining that only one of these is correct (like scientists). I diagnose this situation as reflecting that we are presently quite far from the end of inquiry into philosophical methodology. The good news is that we appear to be making advances on this score. The bad news is that failure to recognize or make explicit that our standards are in flux often leads to dogmatism, as I illustrate by attention to three assumptions presently operative in metaphysical and metametaphysical contexts. I close by identifying a tension between vertical and horizontal progress in philosophy, and suggesting an updated version of Carnap's principle of tolerance for new philosophical forms.

Here I compare two accounts of metaphysical indeterminacy (MI): first, the 'meta-level' approach described by Elizabeth Barnes and Ross Cameron in the companion to this paper, on which every state of affairs (SOA) is itself precise/determinate, and MI is a matter of its being indeterminate which determinate SOA obtains; second, my preferred 'object-level' determinable-based approach, on which MI is a matter of its being determinate---or just plain true---that an indeterminate SOA obtains, where an indeterminate SOA is one whose constitutive object has a determinable property, but no unique determinate of that determinable. In S1, I first note an important difference between our accounts, concerning whether MI is taken to induce propositional indeterminacy; in S2, I highlight and defend certain advantages of my account; in S3, I address certain of Barnes and Cameron's objections to my account.

Some claim that Non- reductive Physicalism is an unstable position, on grounds that NRP either collapses into reductive physicalism, or expands into emergentism of a robust or ‘strong’ variety. I argue that this claim is unfounded, by attention to the notion of a degree of freedom—roughly, an independent parameter needed to characterize an entity as being in a state functionally relevant to its law-governed properties and behavior. I start by distinguishing three relations that may hold between the degrees of freedom needed to characterize certain special science entities, and those needed to characterize their composing physical entities; these correspond to what I call ‘reductions’, ‘restrictions’, and ‘eliminations’ in degrees of freedom. I then argue that eliminations in degrees of freedom, in particular—when strictly fewer degrees of freedom are required to characterize certain special science entities than are required to characterize their composing physical entities—provide a basis for making sense of how certain special science entities can be both physically acceptable and ontologically irreducible to physical entities

Alberto Casullo ("Necessity, Certainty, and the A Priori", Canadian Journal of Philosophy 18, 1988) argues that arithmetical propositions could be disconfirmed by appeal to an invented scenario, wherein our standard counting procedures indicate that 2 + 2 != 4. Our best response to such a scenario would be, Casullo suggests, to accept the results of the counting procedures, and give up standard arithmetic. While Casullo's scenario avoids arguments against previous "disconfirming" scenarios, it founders on the assumption, common to scenario and response, that arithmetic might be independent of standard counting procedures. Here I show, by attention to tallying as the simplest form of counting, that this assumption is incoherent: given standard counting procedures, then (on pain of irrationality) arithmetical theory follows.

Many contemporary philosophers accept Hume's Dictum, according to which there are no metaphysically necessary connections between distinct, intrinsically typed entities. Tacit in Lewis 's work is a potential motivation for HD, according to which one should accept HD as presupposed by the best account of the range of metaphysical possibilities---namely, a combinatorial account, applied to spatiotemporal fundamentalia. Here I elucidate and assess this Ludovician motivation for HD. After refining HD and surveying its key, recurrent role in Lewis ’s work, I present Lewis ’s appeal to HD as providing a broadly axiomatic generating basis for the space of metaphysical modality, and canvas the prima facie advantages of the resulting combinatorial principle---HD ---as being principled, extensionally adequate and modally reductive. Most criticisms of Lewis 's combinatorialism have targeted seeming ways in which the theory overgenerates the desired space; I rather argue that HD seriously undergenerates the desired space in three different ways. For each way I argue that available means of overcoming the undergeneration either fail to close the gap, undermine the claim that HD is a principled generator of metaphysical modal space, undermine the reductive status of Lewis 's combinatorialism, or call into question the truth of HD

Contemporary philosophers commonly suppose that any fundamental entities there may be are maximally determinate. More generally, they commonly suppose that, whether or not there are fundamental entities, any determinable entities there may be are grounded in, hence less fundamental than, more determinate entities. So, for example, Armstrong takes the physical objects constituting the presumed fundamental base to be “determinate in all respects” (1961, 59), and Lewis takes the properties characterizing things “completely and without redundancy” to be “highly specific” (1986, 60). Here I look at the usually cited reasons for these suppositions as directed against the case of determinable properties, in particular, and argue that none is compelling (Sections 1 to 3). The discussion in Section 3 moreover identifies positive reason for taking some determinable properties to be part of a fundamental (or relatively fundamental) base. I close (Section 4) by noting certain questions arising from the possibility of fundamental determinables, as directions for future research.

Grounding, understood as a primitive posit operative in contexts where metaphysical dependence is at issue, is not able on its own to do any substantive work in characterizing or illuminating metaphysical dependence---or so I argue in 'No Work for a Theory of Grounding' (Inquiry, 2014). Such illumination rather requires appeal to specific metaphysical relations---type or token identity, functional realization, the determinable-determinate relation, the mereological part-whole relation, and so on---of the sort typically at issue in these contexts. In that case, why posit 'big-G' Grounding in addition to the 'small-g' grounding relations already in the metaphysician's toolkit? The best reasons for doing so stem from the Unity argument, according to which the further posit of Grounding is motivated as an apt unifier of the specific relations, and the Priority argument, according to which Grounding is needed in order to fix the direction of priority of the specific relations. I previously considered versions of these arguments, and argued that they did not succeed; in two papers, however, Jonathan Schaffer aims to develop a better version of the Unity argument, and offers certain objections to my reasons for rejecting the Priority argument. Here I consider these new arguments for Grounding.

I first discuss Kit Fine's distinctive 'schema-based' approach to metaphysical theorizing, which aims to identify general principles accommodating any intelligible application of the notion(s), by attention to his accounts of essence and dependence. I then raise some specific concerns about the general principles Fine takes to schematically characterize these notions. In particular, I present various counterexamples to Fine's essence-based account of ontological dependence. The problem, roughly speaking, is that Fine supposes that an object's essence makes reference to just what it ontologically depends on, but various cases suggest that an object's essence can also make reference to what ontologically depends on it. As such, Fine's account of ontological dependence is subject to the same objection he raises against modal accounts of essence and dependence---that is, of being insufficiently ecumenical.

Hume's Dictum (HD) says, roughly and typically, that there are no metaphysically necessary connections between distinct, intrinsically typed, entities. HD plays an influential role in metaphysical debate, both in constructing theories and in assessing them. One should ask of such an influential thesis: why believe it? Proponents do not accept Hume's arguments for his dictum, nor do they provide their own; however, some have suggested either that HD is analytic or that it is synthetic a priori (that is: motivated by intuitions we have no good reason to question). Here I explore whether belief in HD is directly justified on either grounds. I motivate and present more formal characterizations of HD; I show that there are good prima facie cases to be made for HD's being analytic and for its being synthetic a priori; I argue that each of the prima facie cases fails, some things considered. I close by offering two suggestions for how belief in HD might be indirectly justified on argumentative grounds.

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.

I address the question of whether there is any role for metaphysics to play on which it is both non-redundant and capable of genuinely illuminating whatever subject matter is at issue. I first argue that metaphysical methodology itself obliges metaphysicians to take this question seriously. I then argue that the currently popular “hands-off” conception of metaphysical theorizing is unable to provide a satisfactory answer to the question of metaphysics. Third, I present my preferred “embedded” conception of metaphysics, and say why it makes good sense of metaphysics as a non-redundant discipline, capable of producing intelligible and illuminating results.

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.

Motivated by the seeming structure of the sciences, metaphysical emergence combines broadly synchronic dependence coupled with some degree of ontological and causal autonomy. Reflecting the diverse, frequently incompatible interpretations of the notions of dependence and autonomy, however, accounts of emergence diverge into a bewildering variety. Here I argue that much of this apparent diversity is superficial. I first argue, by attention to the problem of higher-level causation, that two and only two strategies for addressing this problem accommodate the genuine emergence of special science entities. These strategies in turn suggest two distinct schema for metaphysical emergence---'Weak' and 'Strong' emergence, respectively. Each schema imposes a condition on the powers of entities taken to be emergent: Strong emergence requires that higher-level features have more token powers than their dependence base features, whereas Weak emergence requires that higher-level features have a proper subset of the token powers of their dependence base features. Importantly, the notion of “power” at issue here is metaphysically neutral, primarily reflecting commitment just to the plausible thesis that what causes an entity may bring about are associated with how the entity is---that is, with its features

Here we challenge the orthodoxy according to which abduction is an a posteriori mode of inference. We start by providing a case study illustrating how abduction can justify a philosophical claim not justifiable by empirical evidence alone. While many grant abduction's epistemic value, nearly all assume that abductive justification is a posteriori, on grounds that our belief in abduction's epistemic value depends on empirical evidence about how the world contingently is. Contra this assumption, we argue, first, that our belief in abduction’s epistemic value is not and could not be justified a posteriori, and second, that attention to the roles experience plays in abductive justification supports taking abduction to be an a priori mode of inference. We close by highlighting how our strategy for establishing the a priority of abduction positively contrasts with strategies in Bonjour (1998), Swinburne (2001), and Peacocke (2004) aiming to establish the a priority of certain ampliative modes of inference or abductive principles.

Free will, if such there be, involves free choosing: the ability to mentally choose an outcome, where the outcome is 'free' in being, in some substantive sense, up to the agent of the choice. As such, it is clear that the questions of how to understand free will and mental causation are connected, for events of seemingly free choosing are mental events that appear to be efficacious vis-a-vis other mental events as well as physical events. Nonetheless, the free will and mental causation debates have proceeded largely independently of each other. Here we aim to make progress in determining how the free will and mental causation debates bear on one another. We first argue that the problems of free will and of mental causation can be seen as special cases of a more general problem, concerning whether and how mental events of a given type may be efficacious, qua the types of event they are---qualitative, intentional, freely deliberative---given their apparent causal irrelevancy for effects of the type in question; here we generalize what Horgan 1989 identifies as "the problem of mental quausation" (S1). We then build on this result to identify fruitful parallels between hard determinism and eliminative physicalism (S2) and soft determinism and non-reductive physicalism (S3).