Subject Individuation. A Membership Criterion and the Physical Boundary

Where does a Subject physically end? The General Theory of Observation and the Observer requires the relations constituting Cognition to belong to one and the same Subject, but this requirement alone does not determine which physical processes, structures, and components belong to that Subject and which remain external to it. This work develops a criterion for the physical individuation of a system that has already been qualified as a Subject. It shows that spatial proximity, causal interaction, mutual dependence, resource exchange, feedback, or regulation taken separately are insufficient to establish physical membership. Instead, physical membership is grounded in the constitutive organization of the system: in physically distinguishable regulatory relations, the maintenance of regulatory capacities, recurrent dependence in that maintenance, and material openness. The analysis also addresses interacting organized systems. Resource exchange, mutual necessity, and even mutual regulation do not by themselves make two systems one physical individual. A larger physical organization requires the maintenance of the relevant organization to be constitutively integrated across the boundary between them. The resulting framework distinguishes the physical composition and boundary of the Subject from the organization of its Cognition. The cognitive organization may occupy only part of the physical bearer, but it does not constitute a second Subject and does not determine the physical boundary itself. The work therefore supplies a physical-individuation criterion for the Subject while preserving the distinction between Subject qualification and physical realization.