B1: Modality in Physics and in Metaphysics

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This project is based on the thesis that modality has a place in science, and in particular, in physics: Inductive inferences to modal conclusions do not exclusively appear in metaphysics, but are also part of the practices of physics. There are at least four types of modal inductive inferences within physics: From experimental outcomes it is inferred that theories of a certain kind cannot possibly be true (Type 1), whereas alternative theories with respect to a given standard theory are judged to be equally physically possible and their laws to be contingent (Type 2). Two further types of modal inferences concern the fundamentality or non-fundamentality of particular structures as following from their presence in all or only some models of a theory (Type 3), and as a result of theory unification (Type 4). From the perspective of Inductive Metaphysics, the basic premises of metaphysical inferences must be compatible with empirical facts and lower level theories, while their conclusions must not contradict conclusions established by inferences within physics. Two case studies shall provide examples of applied Inductive Metaphysics by means of reflecting the constraints imposed by modal inferences within physics. The first case study concerns the challenge by Weinberg's Spin 2-approach to Quantum Gravity to the ontological status of Riemannian space-time (cf. Type 4). The second case study aims at a theory of laws of nature respecting the minimal constraints for Inductive Metaphysics by affirming their contingency (cf. Type 2), but providing a better grip on causal necessitation than Armstrong's account of laws.