The published Biological Theory paper began with Agency because it shifted attention from what living systems contain to what living systems continually do in order to remain viable.

Genes, metabolism, development, adaptation, cognition, and evolution are all important to understanding living systems. The paper did not deny their significance or propose Agency as a replacement for their established biological explanations. Instead, it asked a different question: how do living systems actively contribute to maintaining or re-establishing the conditions compatible with their own continued existence?

The paper called this viability-oriented activity biological Agency.

This made Agency its principal explanatory entry point. Living systems regulate, repair, reorganise, and coordinate activity under changing conditions, and the paper proposed that this active relationship to viability was fundamental to understanding Life.

Subsequent APS research has retained that central insight while refining its theoretical role. APS now distinguishes Life, understood as viability-oriented, constraint-closed organisation, from Agency, understood as the viability-oriented activity of that organisation. Agency therefore remains central without being required to provide the complete definition of Life or the sole explanation of organised persistence.

APS Principle: The original paper began with what living systems continually do to remain viable. Current APS retains that Agency insight while locating it within a more differentiated account of living organisation.