Inheritance, fitness, and natural selection are often discussed together, but they do not explain the same phenomenon. APS distinguishes them because each occupies a different position within the continuity architecture of evolutionary organisation.
Inheritance concerns the reliable reconstitution of persistence-sustaining organisation across generations. Through inheritance, viable organisation is repeatedly regenerated despite continual material turnover, developmental transformation, and environmental change. Inheritance therefore explains how continuity is maintained through time.
Fitness concerns differences in continuity among forms of inherited organisation. Some forms of persistence-sustaining organisation contribute more effectively to future continuity than others under particular developmental and ecological conditions. Fitness identifies these differences in continuity. It does not create continuity but reflects differences in the capacity of inherited organisation to remain historically continuous.
Natural selection concerns the differential historical stabilisation of those differences in continuity. Selection does not generate inherited continuity, nor does it create fitness. Rather, it operates upon historically existing differences among forms of organised persistence, influencing which forms contribute more successfully to future continuity across populations and generations.
These processes therefore form a sequence rather than competing explanations. Inheritance reproduces continuity. Fitness reflects differences in continuity. Natural selection differentially stabilises those differences through evolutionary time. Together they connect organised persistence in the present to evolutionary transformation across generations.