*Monadism and Physicalism* argues that neither reductive nor non-reductive physicalism adequately explains the mind-matter relation, especially mental causation. The book defends **elementary dualism**, according to which mind and matter have equal ontological status, and develops a **monadist (substantivalist)** ontology inspired by Leibniz and Whitehead. On this view, mental and physical elements are **mereological components** of unified substances (monads), rather than one supervening asymmetrically on the other. By reworking holism, merology, and substance theory, the book aims to preserve mental realism while avoiding epiphenomenalism and the instability of standard physicalist accounts, ultimately proposing a reconciliation between a refined monadism and a compatible physical ontology.