Our society is saturated with complexity, yet it functions with extraordinary coherence—not by design, but through the continuous collective activity of human beings. At the heart of this coherence lies language: a symbol system that enables coordination, negotiation, and shared meaning-making. Yet the fundamental principles governing how symbols acquire meaning remain unresolved. Two mysteries stand at the core of symbolic communication: the operational closure of individual agents, who cannot directly access each other's inner states, and the inherent arbitrariness of symbols themselves. Symbol emergence systems theory addresses these challenges by framing language as a dynamic equilibrium system sustained through micro–macro loops—bottom-up organization from embodied interactions and top-down constraints from emergent symbol systems. This framework also considers the conditions under which artificial agents could participate in such systems, opening the way for interdisciplinary inquiry spanning AI, robotics, semiotics, phenomenology, and the cognitive sciences.