In biology, function is often understood either as the effect for which a trait was selected or as any causal contribution to a system’s activity. In APS, these accounts are reinterpreted rather than rejected. Function is the contribution of a component or process to the continued viability of the system in which it is embedded.
Because living systems must actively sustain their own persistence, not all effects count as functions. A process has a function only insofar as it contributes to the maintenance of viability within a constraint-closed organisation. Function is therefore grounded in present organisation, while evolutionary history explains how such contributions arise and are stabilised over time.
This allows function to be identified wherever viability-oriented organisation exists, including systems without evolutionary history.
Key Point. Function in APS is not mere effect or selection history—it is the viability-relative contribution of a component within an organised system.