Many discussions of agency treat it as a property that organisms possess. From this perspective, agency can appear analogous to characteristics such as size, complexity, or behavioural capacity, and the central question becomes whether a particular system has agency and, if so, how much.
APS takes a different approach.
Biological agency is not primarily something a living system has. It is something a living system does.
Biological agency is viability-oriented organisational activity.
Living systems persist through continuing activity. Resources are acquired and transformed, internal conditions are regulated, damage is repaired, organisation is renewed, and changing environmental conditions are accommodated. These activities differ among organisms and mechanisms, but they contribute to the continuing maintenance and re-establishment of conditions required for viability.
Agency should therefore be understood as activity rather than as a static property or internal faculty. Living organisation is continually enacted through activity that maintains and re-establishes conditions of its own persistence. When that viability-oriented organisation irreversibly ceases, biological agency has ceased even though some structures, processes, or components may temporarily remain.
This does not mean that every component or process contributing to self-maintenance is itself an agent. A molecular process, regulatory constraint, cell, tissue, or other subsystem may participate in the organisation through which agency is enacted without thereby constituting an independently attributable agent. Agency attribution requires asking whether the candidate system itself instantiates viability-oriented organisation through activity that maintains or re-establishes conditions of its own persistence.
Nor does agency attribution depend upon assigning a candidate to a particular hierarchical level or spatial extent. Scale asks where persistence relevant to the explanandum is organised across spatial and temporal extents; it does not determine where agents occur.
APS Principle: Biological agency is not a property possessed by living systems. It is viability-oriented organisational activity through which living systems maintain and re-establish conditions of their own persistence.
Attribution guardrail: Participation in the organisation through which agency is enacted does not by itself establish an independent biological agent.