Jonathan Schaffer

On the truthmaker view of ontological commitment [Heil (From an ontological point of view, 2003); Armstrong (Truth and truthmakers, 2004); Cameron (Philosophical Studies, 2008)], a theory is committed to the entities needed in the world for the theory to be made true. I argue that this view puts truthmaking to the wrong task. None of the leading accounts of truthmaking—via necessitation, supervenience, or grounding—can provide a viable measure of ontological commitment. But the grounding account does provide a needed constraint on what is fundamental. So I conclude that truthmaker commitments are not a rival to quantifier commitments, but a needed complement. The quantifier commitments are what a theory says exists, while the truthmaker commitments are what a theory says is fundamental.

According to a line of thought tracing from Descartes, Leibniz, and Locke through to Kripke, Levine, and Chalmers, there is a special explanatory gap arising between the physical and the phenomenal. I argue that the physical-phenomenal gap is not special but rather that such gaps are pervasive, lurking in the transition from the physical to the chemical and in every concrete transition from more to less fundamental. Correlatively, I argue that such gaps are unproblematic, so long as they are bridged by substantive principles of metaphysical grounding. So I articulate a form of physicalism — “ground physicalism” — on which the physical grounds the chemical, the biological, and the psychological, and explain how ground physicalism resolves explanatory gap worries.

Kaplan (drawing on Montague and Prior, inter alia) made explicit the idea of world and time neutral propositions, which bear truth values only relative to world and time parameters. There was then a debate over the role of time. Temporalists sided with Kaplan in maintaining time neutral propositions with time relative truth values, while eternalists claimed that all propositions specify the needed time information and so bear the same truth value at all times. But there never was much of a parallel debate over the role of worlds. Let contingentism be the view (parallel to temporalism) that sides with Kaplan in maintaining world neutral propositions with world relative truth values, and let necessitarianism be the view (parallel to eternalism) that propositions specify the needed world information and so bear the same truth value at all worlds. This is the story of how the debate between the contingentists and the necessitarians might begin.

What knowledge is imperilled by sceptical doubt? That is, what range of beliefs may be called into doubt by sceptical nightmares like the Cartesian demon hypothesis? It is generally thought that demons have limited powers, perhaps only threatening a posteriori knowledge of the external world, but at any rate not threatening principles like the cogito. I will argue that there is a demon – the debasing demon – with unlimited powers, which threatens universal doubt. Rather than deceiving us with falsities, the debasing demon would allow us true beliefs, but only as guesses.

What conception of causation is at work in the law? I argue that the law implicitly relies on a contrastive conception. In a liability case where the defendant's breach of duty must be shown to have caused the plaintiff's damages, it is not enough to consider what would have happened if the cause had not occurredthe law requires us to look to a specific replacement for the effect, which in this case is the hypothetical outcome in which the plaintiff came off better. In place of I suggest the more explicit An explicitly contrastive approach can thus potentially help the lawyer phrase her causal question in a more explicit way, while shedding light on our conception of causation

Metaphysical semantics is supposed to connect the nonfundamental to the fundamental in a distinctively “linguistic” way, explaining how nonfundamental truths can be grounded in fundamental facts , and so inducing a radically eliminative vision of the nonfundamental as mere talk. I wonder how the story goes when a single nonfundamental truth can be grounded in many different fundamental facts. For instance, the truth that Moore has hands can presumably be grounded in many different distributions of fields, arrangements of particles, vibrations of strings, or whatnot. I am asking how metaphysical semantics can accommodate this sort of multiple realizability

Questions about the metaphysics of causation may be usefully divided as follows. First, there are questions about the nature of the causal relata, including (1.1) whether they are in spacetime immanence), (1.2) how fine grained they are individuation), and (1.3) how many there are adicity). Second, there are questions about the metaphysics of the causal relation, including (2.1) what is the difference between causally related and causally unrelated sequences connection), (2.2) what is the difference between sequences related as cause to effect, and those related as effect to cause or as joint effects of a common cause direction), and (2.3) what is the difference between sequences involving the cause, and those involving mere conditions selection).

Quantum mechanics seems to portray nature as nonseparable, in the sense that it allows spatiotemporally separated entities to have states that cannot be fully specified without reference to each other. This is often said to implicate some form of “holism.” We aim to clarify what this means, and why this seems plausible. Our core idea is that the best explanation for nonseparability is a “common ground” explanation, which casts nonseparable entities in a holistic light, as scattered reflections of a more unified underlying reality.

Feminist metaphysics is guided by the insight that gender is socially constructed, yet the metaphysics behind social construction remains obscure. Barnes and Mikkola charge that current metaphysical frameworks—including my grounding framework—are hostile to feminist metaphysics. I argue that not only is a grounding framework hospitable to feminist metaphysics, but also that a grounding framework can help shed light on the metaphysics behind social construction. By treating social construction claims as grounding claims, the feminist metaphysician and the social ontologist both gain a way to integrate social construction claims into a general metaphysics, while accounting for the inferential connections between social construction and attendant notions such as dependence and explanation. So I conclude that a grounding framework can be helpful for feminist metaphysics and social ontology.

Knowledge ascriptions are contrast-sensitive. One natural explanation for this is that the knowledge relation is contrastive ( s knows that p rather than q ). But can the binary view of knowledge ( s knows that p ) explain contrast-sensitivity? I review some of the linguistic data supporting contrast-sensitivity, and critique the three main binary explanations for contrast-sensitivity. I conclude that the contrast-sensitivity of knowledge ascriptions shows that knowledge is a contrastive relation