APS distinguishes between organisation, agency, and viability while treating them as inseparable aspects of living systems.
Organisation refers to the structured relations through which biological processes collectively maintain a living system. Organisational closure, regulation, and coordination allow organisms to preserve their integrity despite continual material turnover and environmental change.
Agency refers to the active engagement of living systems with conditions affecting their continued existence. Organisms do not merely undergo processes; they act. Through behaviour, physiological adjustment, environmental modification, development, and reproduction, they contribute to the maintenance of favourable conditions for persistence.
Viability refers to the conditions under which organised persistence remains possible. Living systems continuously distinguish between states that support continued existence and states that undermine it. This distinction grounds biological normativity because some activities contribute to viability while others threaten it.
These concepts form a nested explanatory relationship. Organisation provides the conditions under which agency becomes possible. Agency contributes to the maintenance of viability. Viability supplies the normative horizon through which organisational and agentive activity acquire biological significance.
APS therefore understands living systems not simply as organised entities, nor merely as agents, but as viability-oriented forms of organised persistence whose agency contributes to the maintenance of the conditions required for continued existence.
See also: [[glossary:biological-agency]], [[glossary:viability]], [[glossary:constraint-closure]]