This article serves as an exegesis of George Herbert Mead’s utilization of Einstein’s relativity theory, a theory Mead utilized to support and develop his own theory of partially self-determining, perspectival agency. The article provides a brief conceptual explanation of relativity theory, outlines the key concepts Mead took from relativity theory, explains how Mead applied these concepts to his own philosophy, and attempts to evaluate the relevance of Mead’s application of relativity theory to his philosophy as a whole. Mead sought to develop a unified perspectival ontology in which agentive perspectives were embedded within the fabric of a perspectival universe. This article argues that Mead did not succeed in achieving such a unified perspectival ontology. Nonetheless, many aspects of his argument remain relevant to current debates on self-determining human agency.