This thesis contributes to the development of a ‘neo-Aristotelian’ ontology of powers that accommodates quantum phenomena. It offers a number of philosophical objections to ‘Super-Humean’ metaphysics, and constructs a sequence of models that aim to improve upon it, using the metaphysical toolbox constructed in Part I.

In Part II, I explore how quantum entanglement challenges the ‘classical’ conception of the world as consisting of particles (or fields) with intrinsic physical properties (Chapter 3). I consider the metaphysical model offered by Super-Humeanism, which accommodates entanglement by combining a ‘primitive ontology approach’ to quantum mechanics with ontic structural realism (Chapter 4). According to Super-Humeans, the world is made of matter points constituted by distance relations. I raise three objections to its structuralist conception of matter. I then propose an alternative semi-Humean model, ‘Bohmian power structuralism’, which overcomes these objections through an ontology of ‘power-atoms’ with multi-track causal powers (Chapter 5). But its Humean conception of laws can be challenged. A second model, ‘power monism’, enriches the primitive ontology to include a ‘cosmic power’ that transforms the power-atoms into a cosmic whole, and supports an Aristotelian-essentialist conception of laws (Chapter 6). This model overcomes the difficulties with power structuralism, but is susceptible to Hawthorne’s ‘extrinsicality’ argument, excluding consciousness from the physical world.

In Part III, I consider the emergence of thermochemical properties within macroscopic (or mesoscopic) quantum systems. Metaphysical models that incorporate only finite degrees of freedom, like Super-Humeanism, cannot accommodate properties like temperature and chemical entropy, which are represented in physics in the ‘thermodynamic limit’ (Chapter 7). I offer an additional argument against adopting a reductionist approach based on Putnam’s ‘permutation argument’ (Chapter 8). Finally, I outline a third model, ‘power pluralism’, in which the world consists of: a substrate of ‘power-gunk’, and ‘substantial powers’ that elicit substances from the power-gunk (Chapter 9). In this model, quantum-entangled microscopic particles are potential parts of macroscopic (or mesoscopic) substances, which have intrinsic thermochemical properties.