Introduction

The paper Agency as the Defining Activity of Life: A Viability-Oriented Framework Integrating Process and Scale, published in Biological Theory, began from a familiar but difficult biological question: what distinguishes a living system from a nonliving one?

Rather than beginning with a list of characteristic structures or capacities, the paper focused on activity. Living systems regulate internal conditions, maintain boundaries, repair damage, reorganise in response to disturbance, and continually contribute to conditions under which their organisation can continue. The paper called this viability-oriented activity biological Agency and proposed it as the defining activity of Life (Spencer 2026).

That formulation remains important, but it raises a question that subsequent development of APS makes possible to state more precisely. If Life is viability-oriented, constraint-closed organisation, and biological agency is viability-oriented organisational activity, in what sense can Agency still be described as the defining activity of Life?

The answer requires distinguishing two closely related questions:

What is Life?

and

What is distinctive about the activity of living organisation?

APS does not now give these questions the same answer. Life identifies a form of organisation. Agency identifies what that organisation does in relation to viability. The distinction does not diminish the importance of Agency. It clarifies why Agency can be the defining activity of Life without being the complete definition of Life.

Where This Article Fits

This article is a clarification of the Agency thesis first developed in the published Biological Theory paper. Its purpose is not to provide the general APS account of biological Agency. That role belongs to Biological Agency as the Activity of Self-Maintenance, the Anchor article for the APS Agency corpus.

The present article addresses a narrower question: what does it mean to call Agency the defining activity of Life?

Answering that question requires representing the published thesis accurately while distinguishing it from the subsequently clarified APS architecture. The original paper gave Agency a particularly strong theoretical role. Current APS retains its central insight while distinguishing more carefully between Life as viability-oriented, constraint-closed organisation and Agency as the viability-oriented organisational activity of that living organisation.

This article therefore connects a fixed published stage in the development of APS with the framework’s current formulation. It does not independently redefine Agency, provide criteria for agency attribution, develop the full relationship between Agency and organised persistence, or compare APS with contemporary theories of biological agency. Those questions are addressed elsewhere in the Agency corpus.

Its concern is one claim: Agency can remain the defining activity of Life without Agency becoming the definition of Life itself.

1. The Published Agency Thesis

The published paper approached Life through what living systems do.

Cells and organisms undergo continual material and organisational change. Components are produced, transformed, damaged, repaired, and replaced. Internal conditions fluctuate. Environmental circumstances change. Yet living systems can maintain a form of organised continuity through these transformations.

The paper argued that this persistence is not adequately characterised as passive endurance. Living systems actively contribute to maintaining and re-establishing conditions compatible with their continued existence. Regulation, repair, boundary maintenance, responsiveness, and reorganisation are biologically diverse activities, but they can all bear upon the viability of the system performing them.

The paper used Agency to bring this activity into explanatory focus. Agency did not mean consciousness, intelligence, deliberate choice, or human-like intention. It referred to viability-oriented activity through which living systems sustain and reconstitute their organisation across time and changing conditions (Spencer 2026).

That was the sense in which Agency was proposed as the defining activity of Life.

The claim was deliberately stronger than the observation that organisms happen to regulate themselves. It proposed that active contribution to the conditions of continued viability is fundamental to the kind of organisation characteristic of living systems. A rock can persist without acting to maintain the conditions under which it remains a rock. Living systems persist differently: their continuation depends upon organised activity through which conditions relevant to their viability are continually maintained, restored, or altered.

The paper therefore shifted attention from a catalogue of what living systems possess to the organisation of what living systems do.

It also sought to make this proposal empirically tractable. The paper proposed biosignatures including homeostasis, adaptive plasticity, selective boundary regulation, goal-directed behaviour, recursive self-repair, and cross-scale coordination as possible indicators of viability-oriented activity, while acknowledging unresolved questions about thresholds, borderline cases, and nonliving self-organisation (Spencer 2026).

The published proposal should be understood in that context. It was not an attempt to introduce Agency as an additional causal force alongside metabolism, physiology, development, or molecular regulation. It sought to redescribe established biological activity in relation to the organisational conditions under which living systems continue to exist.

Its central thesis can therefore be stated simply:

Living systems do not merely persist. They actively contribute to maintaining and re-establishing conditions compatible with their own continued viability.

The paper called that activity biological Agency.

2. Defining Life and Identifying Its Defining Activity

The phrase defining activity of Life can be misunderstood if defining Life and identifying the characteristic activity of living organisation are treated as the same task.

APS now distinguishes them.

Life is viability-oriented, constraint-closed organisation.

This is the canonical APS definition of Life. It identifies living organisation in terms of the relation between viability and constraint closure rather than by reducing Life to a list of traits or to any single activity.

Biological agency is viability-oriented organisational activity.

Agency therefore answers a different question. It asks what living organisation does in relation to conditions relevant to its continued functioning.

The distinction can be expressed compactly:

Life identifies the organisation. Agency identifies its viability-oriented activity.

This does not divide biological reality into a living organisation on one side and an independent thing called Agency on the other. Agency exists only as activity of materially realised living organisation. Conversely, living organisation is not a static arrangement that merely possesses Agency as an optional property. Its continuation depends upon ongoing activity.

Agency is therefore an analytic projection of living organisation rather than an additional component or cause within it.

This distinction resolves an ambiguity that arises if Agency is asked simultaneously to answer what Life is and what living systems do. If Agency is defined through the activity of living systems and Life is then defined solely through Agency, the two concepts risk becoming circular. Distinguishing organisation from activity gives each concept a clearer explanatory role.

The result does not require abandoning the title of the published paper.

Agency can be the defining activity of Life because viability-oriented organisational activity characterises the active enactment of living organisation without Agency having to provide the complete definition of that organisation.

3. Why Agency Remains Defining

Calling Agency defining makes a stronger claim than saying that living systems exhibit activity.

All physical systems undergo change, and many nonliving systems participate in complex causal processes. Biological Agency cannot therefore be identified simply with activity, change, causation, responsiveness, or complexity.

The relevant activity is viability-oriented organisational activity.

Viability introduces an asymmetry among conditions. Some changes contribute to maintaining or re-establishing conditions under which the organisation can continue functioning; others impair or destroy those conditions. Agency concerns activity organised relative to this difference.

This is why repair is biologically significant in a way that arbitrary molecular change is not. It is why regulation can be analysed in relation to conditions of continued functioning rather than merely as one causal sequence among others. It is also why biological Agency need not imply conscious evaluation. The relevant asymmetry is grounded in the viability of the living organisation.

Constraint closure adds a further organisational condition. Living systems depend upon constraints that regulate processes while themselves being generated, maintained, or re-established through the organisation in which they operate. Agency occurs within this viability-oriented, constraint-closed organisation; it does not substitute for it.

The claim that Agency is defining should therefore not be read as:

Life = Agency.

Nor should it be read as:

Agency is the fundamental causal force producing living organisation.

The defensible claim is more precise:

Living organisation is distinctive in part because its continuing organisation is enacted through viability-oriented organisational activity. Agency is the APS analytic projection that brings this activity into explanatory focus.

That is sufficient for Agency to remain the defining activity of Life.

4. Agency and Organised Persistence

The original Agency thesis was closely connected to persistence. Living systems continually undergo change while maintaining forms of organised continuity, and the published paper emphasised that such persistence is an ongoing achievement rather than passive endurance (Spencer 2026).

That insight remains.

What requires clarification is the relationship between Agency and the phenomenon being explained.

Organised persistence is the continuity of living organisation through change. Components turn over, internal states fluctuate, damage occurs, development alters organisation, and environmental conditions vary. Yet living organisation can continue through these transformations.

Agency contributes to explaining that persistence because living systems engage in viability-oriented organisational activity. Repair, regulation, reorganisation, boundary maintenance, and other activities can materially contribute to maintaining or re-establishing conditions under which living organisation continues.

But organised persistence should not therefore be treated as an output generated by Agency alone.

The full explanation of a particular case may require mechanisms, constraints, temporal relations, environmental conditions, developmental histories, evolutionary histories, or other materially realised dependencies. Agency identifies one explanatory question within that organisation: how does the activity of the living system bear upon viability?

The more detailed relationship between Agency and organised persistence belongs to Agency and Organised Persistence. The important point here is narrower. Describing Agency as the defining activity of Life does not make Agency the sole cause or complete explanation of living persistence.

It identifies the characteristic viability-oriented activity through which living organisation participates in maintaining and re-establishing conditions of its continuation.

5. Agency within the APS Architecture

The published paper brought Agency, Process, and Scale together within a common framework. Subsequent development has clarified how these terms should be related.

They are not a sequence:

Agency → Process → Scale

They are not independent components of Life, and they are not levels of biological organisation.

Agency, Process, and Scale are analytic projections of one viability-oriented, constraint-closed organisation.

Agency asks what living systems do: it brings viability-oriented organisational activity into explanatory focus.

Process asks how continuity is maintained despite change.

Scale asks where persistence relevant to an explanandum is organised across spatial and temporal extents.

The distinctions are analytic, but they concern materially realised biological organisation. They allow different explanatory questions to be directed towards the same living system without turning those questions into separate entities or causes.

This matters for the defining-activity thesis because Agency need not be made foundational to Process and Scale in order to remain biologically fundamental. Calling Agency the defining activity of Life does not mean that every biological explanation must begin with Agency or ultimately reduce to it.

It means that when the explanatory question concerns what living organisation does in relation to its viability, Agency identifies the relevant analytic projection.

The published thesis can therefore be retained without an Agency-first architecture.

6. What the Original Thesis Establishes

The clarification developed here allows the surviving content of the original thesis to be stated without either weakening it into a trivial observation or asking it to establish more than it can support.

The first claim is that living organisation is active. Living systems continually participate in maintaining and re-establishing conditions relevant to their own viability.

The second is that this activity is viability-oriented. Biological changes are not equivalent with respect to the continuation of the living organisation.

The third is that this activity does not require conscious intention, deliberation, intelligence, or cognition. Those capacities may occur in some forms of life, but they are not constitutive of biological Agency.

The fourth is that Agency is organisational rather than an additional causal force. An agential analysis does not replace the molecular, physiological, developmental, ecological, or other mechanisms through which biological activity is materially realised.

The fifth is that calling Agency the defining activity of Life does not establish that Agency provides explanatory gain for every biological explanandum. A warranted Agency analysis and a demonstrated explanatory contribution are different claims. Where explanatory gain is claimed, it must be assessed relative to the specified target and the strongest relevant comparator.

The original paper’s central insight can therefore survive while its explanatory burden becomes more precisely bounded.

7. Why the Title Still Holds

The question with which this article began can now be answered directly.

If Life is viability-oriented, constraint-closed organisation, why call Agency the defining activity of Life?

Because living organisation is not merely a configuration that happens to endure. Its continuation is continually enacted through activity occurring in relation to conditions of viability. Biological Agency names that viability-oriented organisational activity.

The distinction between Life and Agency therefore does not separate two independent biological realities.

Life identifies the organisation.

Agency identifies what that living organisation does in relation to viability.

The published paper was right to make this activity central. What subsequent clarification adds is a more exact account of the theoretical work the concept should perform.

Agency does not need to define the whole of Life in order to identify its defining activity. It does not need to generate organised persistence by itself. It does not need to stand above Process or Scale. And it does not need to replace established biological mechanisms or explanations.

Its role is both narrower and clearer:

Biological agency is viability-oriented organisational activity. It is the defining activity of Life because living organisation is continually enacted through activity that maintains and re-establishes conditions relevant to its own viability.

That is the strongest continuing interpretation of the original Agency thesis.

Conclusion

Agency as the Defining Activity of Life proposed that understanding living systems requires attention not only to what they contain or which traits they display, but to the activity through which they contribute to maintaining the conditions of their own continued existence.

That central insight remains part of APS.

The developed framework now distinguishes the organisational definition of Life from the activity of living organisation:

Life is viability-oriented, constraint-closed organisation.

Biological agency is viability-oriented organisational activity.

These formulations answer related but different questions. The first identifies the organisation characteristic of Life. The second identifies its viability-oriented activity.

Organised persistence, meanwhile, identifies a phenomenon requiring explanation: the continuity of living organisation despite material, environmental, and organisational change. Agency can contribute to such explanations without becoming their sole cause or sufficient explanation.

Agency, Process, and Scale likewise need not form an Agency-first sequence. They are analytic projections of one living organisation rather than components of biological reality.

The title of the published paper can therefore be retained in a precise sense. Agency is not the complete definition of Life. It is the defining activity of Life because viability-oriented organisational activity is characteristic of how living organisation continually maintains and re-establishes conditions of its own continuation.

The distinction preserves the central Agency thesis while making clear what Agency identifies, what it does not replace, and what further work is required whenever an Agency analysis claims explanatory gain.

Explanatory Architecture

Central Question

In what precise sense can biological Agency be described as the defining activity of Life when Life itself is defined as viability-oriented, constraint-closed organisation?

Architectural Role

This article is a Clarification article within the Conceptual Foundations cluster.

Its function is to interpret and delimit the thesis first developed in Agency as the Defining Activity of Life: A Viability-Oriented Framework Integrating Process and Scale (Spencer 2026).

The article distinguishes the definition of Life from the identification of its defining activity. Life identifies viability-oriented, constraint-closed organisation; Agency identifies the viability-oriented organisational activity of that living organisation.

Relationship to the Agency Anchor

Biological Agency as the Activity of Self-Maintenance is the canonical Agency Anchor. It establishes what biological Agency is, the conditions governing its attribution, its distinction from explanatory Scale, and the difference between warranted Agency attribution and demonstrated explanatory gain.

The present article does not duplicate those functions.

It asks instead why Agency, once defined and bounded by the Anchor, can properly be described as the defining activity of Life.

Relationship to Organised Persistence

Organised persistence is principally a phenomenon requiring explanation rather than an outcome produced by Agency alone.

Agency can contribute to explanations of organised persistence by identifying viability-oriented organisational activity involved in maintaining or re-establishing conditions of continuation. The detailed relationship between these concepts is developed in Agency and Organised Persistence.

Position within APS

Agency, Process, and Scale are analytic projections of one viability-oriented, constraint-closed organisation rather than independent causes, components, stages, dimensions, or levels of biological reality.

Calling Agency the defining activity of Life therefore gives Agency neither hierarchical priority nor universal explanatory priority. It identifies the characteristic viability-oriented activity of living organisation.

Corpus Significance

This article preserves the interpretive connection between the published Biological Theory Agency thesis and the developed APS framework without retrospectively rewriting the published paper.

Its distinctive contribution is the proposition:

Agency can be the defining activity of Life without being the definition of Life.

For the canonical operational account of biological Agency, see Biological Agency as the Activity of Self-Maintenance. For the detailed relationship between Agency and organised persistence, see Agency and Organised Persistence. For the boundary between biological Agency and intention, cognition, and representation, see Biological Agency Without Intentions.