Psychology’s Missing Matter

Psychology's replication and generalizability shortcomings suggest that, although valuable, statistical and incentive reforms have not stabilized core constructs. I argue that residual implicit dualism, characterized by the acceptance of loosely defined constructs supported by metaphors and weakly connected to biologically specific mechanisms, contributes to this instability. I propose the Materialist Model of Psychological Science (MMPS): a pluralism-friendly framework based on four axioms (physical realization, multi-level constraint, evolutionary plausibility and mechanistic falsifiability). These axioms are operationalized via an eight-criterion ontological audit with phase-based governance (from prototype to maturity). When applied to three illustrative cases: ego depletion, implicit bias, and fear conditioning. The audit reveals a systematic link between mechanistic density (material anchoring, perturbation-sensitive predictions, and cross-context invariance) and replication robustness. The paper outlines complementary reforms, such as mechanism-focused preregistration, invariance profiling in multilab work, perturbation toolkits and open construct registries, that redirect theory building towards cumulative, vertically integrated knowledge, while safeguarding exploratory diversity through graded evidential expectations. The MMPS adds explicit mechanistic, evolutionary, and perturbational constraints to classical construct validity. The result is a practical foundation that converts diffuse calls for 'better theory' into concrete, auditable criteria for accepting, revising or suspending psychological construct