Spacetime as a Compatibility-Induced Coordinative Structure

Spacetime is often treated in physical theory as the universal arena within which fields, particles, interactions, and observers are located. Yet descriptive indispensability does not establish ontological fundamentality. This paper argues that spacetime is better understood as a derivative, compatibility-induced coordinative structure rather than as a primitive background. If so, its ground cannot already presuppose full spacetime structure, which gives reason to posit an ontologically prior, non-spatiotemporal basis. The paper introduces projection, invariance, and compatibility as a minimal conceptual vocabulary for articulating this dependence. A shared spacetime regime becomes available only where localization, metric comparability, causal ordering and inter-observer consistency can be jointly maintained. On this basis, familiar issues such as entanglement, measurement, spacetime breakdown, and temporal asymmetry are reinterpreted as illuminating the conditions and limits of spacetime’s applicability.