Within APS, living systems are understood as viability-oriented, constraint-closed organisations whose activity maintains and re-establishes conditions required for continued functioning.
Agency, Process, and Scale are complementary analytic projections of this one organisation. Agency concerns what living systems do. Process concerns how organisational continuity is maintained despite change. Scale concerns across what materially realised spatial and temporal extents, and through what relations among them, persistence is organised.
These projections help formulate different questions about living organisation without determining in advance either the explanandum or what an adequate explanation must contain. APS may ask how viability is maintained, how constraints are mutually sustained, how continuity persists through transformation, or how materially implemented relations across spatial and temporal extents alter local conditions.
Other APS concepts identify more specific explanatory relations. Biological Evaluation concerns the process through which agency generates significance. Function concerns present-tense viability-relative organisational contribution. Purpose concerns viability-oriented organisation without requiring intention or future-directed causation. Cognition requires an organisation of biological significance that goes beyond immediate evaluation or fixed regulation. Evolution concerns historical change and remains explanatorily distinct from the present organisation of living systems.
APS therefore does not treat all biological phenomena as expressions of organised persistence or require every explanation to employ its full conceptual vocabulary. Organised persistence denotes the continuity of living organisation through material and structural transformation. Where APS and another framework address the same explanatory target, any claimed explanatory gain requires target-matched comparison with the strongest relevant alternative.