Newton's Metaphysics of Substance offers a systematic interpretation of Isaac Newton's views on the ontology of substance and related issues of modality, causation, and dependence. Alongside and sometimes in dialogue with his work in mathematics and physics, Newton developed a coherent and unified account of God, material bodies, human minds, and the relations between them. Drawing on a large number of published and unpublished sources, Patrick J. Connolly traces the development of Newton's views, situates them within the wider context of early modern philosophy, and highlights their value and originality.

Newton holds that God is different in kind from created substances. While God has a substantial essence or nature, created substances like bodies and human minds are merely collections of powers. Created substances nonetheless enjoy considerable independence and autonomy. Newton rejects positions like occasionalism which deeply involve God in the immediate production of nature's works. Much of his project, then, involves individuating, defining, and analysing the different powers that join together to account for the phenomena displayed by minds and bodies.

Exploring Newton's understanding of God, bodies, and minds in this way reveals his deep engagement with many of the central philosophical issues considered by his contemporaries. Among other topics, the book canvases Newton's approach to arguments for God's existence, the univocity of being, causation, atomism and infinite divisibility, the architecture of matter, human cognitive faculties, and the mind-body problem. On each of these topics Newton carefully engages the views of his predecessors in the course of developing arguments for his preferred position.

While Newton's work is of continuing interest for philosophy of science, this book shows that his philosophical interests and achievements were much broader. Although he never published a unified treatment of his metaphysical views, it is possible to understand Newton as having constructed a philosophical system. In this sense, he can be usefully situated alongside figures like Descartes, Locke, and Leibniz.