Conceptual Foundations

Biological agency is one of biology's most widely used yet least consistently defined concepts. This article develops a viability-oriented account of biological agency within the Agency–Process–Scale (APS) framework, defining agency as the activity through which living systems continually maintain and re-establish the conditions of their own organised persistence. Agency is understood as self-maintaining organisational activity rather than behaviour, cognition, intention or conscious choice. This account clarifies agency's relationship to viability, organised persistence, function, development, ecology, evolution and biological explanation, establishing biological agency as one of the principal conceptual foundations of APS.

Persistence is one of the deepest organising concepts in APS because living systems remain continuous despite ongoing material, developmental, ecological, and evolutionary change. APS explains persistence not as static endurance but as organised continuity actively maintained through viability-oriented organisation. This article shows how persistence emerges through the coordinated activity of agency, viability, organisation, process, and scale, and why organised persistence provides one of the central explanatory concerns of biology.

Life remains one of biology's most fundamental yet persistently contested questions. Despite extraordinary advances across the biological sciences, no single account of life has achieved broad conceptual agreement. Competing approaches variously emphasise metabolism, reproduction, evolution, information, autonomy, autopoiesis, or organisational closure, each illuminating important aspects of living systems while leaving significant explanatory questions unresolved. This article examines why the question remains open and argues that the continuing debate reflects uncertainty concerning the organisational target of biological explanation. Rather than asking which properties distinguish living systems, the APS framework investigates the kind of organisation that makes those properties possible, proposing that life is best understood as viability-oriented, constraint-closed organisation sustained through organised persistence.

This article establishes the principle that APS concepts form an organised system of mutually constraining definitions. It explains why conceptual closure is required for coherent biological explanation and how this principle stabilises the framework.

This article clarifies what makes explanation distinctively biological by arguing that biological inquiry is ultimately concerned with organised persistence: the capacity of living systems to maintain continuity through continual transformation. APS proposes that viability-oriented, constraint-closed organisation provides the organisational basis through which organised persistence is achieved, sustained, and transformed across time.

Biological organisation is a central target of explanation within APS. Living systems persist despite continual material, functional, developmental, and environmental change because their organisation is actively maintained and re-established. APS characterises living organisation as viability-oriented and constraint-closed, and analyses it through the complementary, target-sensitive analytic projections of Agency, Process, and Scale. This perspective does not replace established biological explanations or reduce biological organisation to a single component, mechanism, or scale. It identifies an organisational target to which different explanatory approaches may contribute.

Constraints are central to biological organisation because they channel activity into continuity-preserving organisation across time. In APS, constraints are not merely limitations or restrictions, but the organised relations through which living systems maintain viable continuity under changing conditions. This article explains how constraints enable organised persistence, how constraint closure produces self-maintaining organisation, how constraints are modulated through biological agency, and how developmental, ecological, and temporal organisation continuously reconstruct constraint relations across interacting scales. APS therefore understands life as viability-oriented organised persistence enacted through dynamically maintained and continuously reconstructed constraint organisation.

Constraint closure is a central concept in contemporary theories of biological organisation, but closure alone does not explain biological persistence, agency, or viability-oriented continuity. APS adopts constraint closure as a necessary condition for organised persistence while clarifying its limits: closure provides the structural basis for self-maintaining organisation, but only temporally organised, viability-oriented activity generates living organisation. This article explains what constraint closure contributes to biological explanation, what it cannot explain on its own, and why APS situates closure within a broader framework of continuity-producing biological organisation.

This article explains how biological normativity arises within the APS framework. APS explains biological normativity as an emergent consequence of viability-oriented organised persistence. Norms, functions, purposes, and meanings are not externally imposed upon living systems but arise through the evaluative organisation required to maintain viability across time. Because biological agents must maintain the conditions of their own persistence, they must evaluate states, actions, and outcomes as more or less supportive of continued organisation. Viability grounds agency, agency requires evaluation, and evaluation generates biological normativity.

Biological functions are commonly understood as the contributions made by particular structures or mechanisms to the operation of living systems. While such analyses explain how individual functions are realised, they do not by themselves explain how living systems continually maintain themselves despite ongoing material turnover, developmental change, physiological reorganisation, and environmental variation. This article argues that biological function is most fully understood as operational organisation. Functions are interpreted as viability-oriented organisational roles whose significance derives from their integration within the continuing activity of the organism. The article develops an operational architecture encompassing temporal organisation, functional integration, mechanistic realisation, constraint modulation, functional equivalence, adaptive reorganisation, distributed functional organisation, and operational persistence. Together these organisational dimensions explain how living systems continually maintain and re-establish the conditions of their own persistence. In doing so, the article complements normative accounts of biological function by providing an integrated account of how biological functions collectively realise the continuing activity of life.

This article introduces biological normativity in APS as the intrinsic, viability-relative asymmetry through which living systems distinguish persistence-supporting from persistence-undermining conditions. Normativity emerges because living systems exist under conditions where organised continuity can succeed or fail. APS therefore explains normativity not as externally imposed value or subjective judgment, but as an organisational feature of viability-oriented persistence enacted through temporally organised biological activity. This article situates normativity within the broader framework of organised persistence explored further in *Function and Normativity — Why Biological Organisation Matters*.

In APS, the organism is not a static entity but a dynamically maintained organisation through which viability-oriented activity is sustained. This article develops the organism as the minimal unity of agency, normativity, and persistence, clarifying its role as the condition for biological organisation and evolutionary dynamics.

APS distinguishes organism, individual, and agent as three complementary but non-equivalent ways of describing biological unity. This article clarifies their relations within viability-oriented, constraint-closed organisation, showing how agency, individuality, and organismal organisation intersect without collapsing into one another.

This article explains process in APS as the dynamic biological organisation through which living systems sustain and transform the constraints that enable their continued viability.

This article explains scale in APS as the spatial and temporal coordination of biological organisation, showing how living systems integrate processes across multiple interacting domains.

This article develops the temporal architecture of the APS framework. APS rejects the treatment of living systems as static entities merely located within external chronological time. Living systems actively organise continuity across time through developmentally and temporally structured processes that continuously regenerate, repair, reorganise, and transform viable organisation across changing conditions and interacting timescales. Biological persistence therefore depends upon continuity through transformation rather than static endurance. Temporal organisation is thus constitutive of biological explanation itself rather than an external background against which life unfolds.

Viability occupies a central organising position within the APS framework. Living systems do not merely survive but actively sustain, regulate, and reconstruct the conditions required for continued persistence across changing conditions. Agency maintains viability, viability enables organised persistence, and organised persistence provides the continuity through which living systems exist across time. This article develops viability as the organisational condition linking agency, persistence, function, normativity, process, scale, development, ecology, and evolution. Within APS, viability is understood not as passive survival or static maintenance but as the organised capacity to preserve continuity through continual transformation.

Biological systems are commonly described in terms of their components, mechanisms, or characteristic properties, yet these descriptions do not by themselves explain what makes a system biological. This article argues that biological systems are distinguished not simply by the mechanisms they contain but by viability-oriented, constraint-closed organisation through which they actively maintain and re-establish the conditions of their own organised persistence. Drawing on the Agency–Process–Scale (APS) framework, the article shows how mechanisms, regulation, repair, organisms, process, and scale become scientifically intelligible when understood as aspects of a single organisational reality. It therefore provides an integrated public explanation of what distinguishes biological systems from other organised physical systems.

The concept of the organism is central to biology, yet often taken for granted or reduced to structural or genetic descriptions. In APS, an organism is not defined by its components but by its organisation: a dynamically integrated, viability-oriented system that actively sustains the conditions of its own persistence. This article introduces the organism as a processual, agential unity emerging from constraint-closed organisation and maintained through ongoing organism–environment coupling.

The paper “Agency as the Defining Activity of Life, . . . ” published in the journal Biological Theory, proposed that biological agency—the viability-oriented activity through which living systems contribute to maintaining the conditions of their own continued existence—is fundamental to understanding life. Subsequent development of the Agency–Process–Scale (APS) framework has retained this central insight while clarifying 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. Organised persistence is treated as a phenomenon requiring explanation, while Agency, Process, and Scale are complementary analytic projections on living organisation rather than a foundational sequence. Subsequent work has also distinguished conceptual integration from demonstrated explanatory gain. This article explains what the original Agency thesis claimed, what subsequent APS research has retained, what has changed, and why those changes matter.

This article clarifies how APS understands biological agency as viability-oriented, normatively structured activity that does not require intention, representation, or mental states. It shows how agency arises from the organisation of living systems and how more complex forms of agency develop without introducing a categorical break.

Biology has traditionally described living systems through hierarchical levels ranging from molecules to ecosystems. While useful for classification and description, hierarchical models often misrepresent the organisation of living systems by treating biological reality as a stack of separate domains. APS replaces hierarchical levels with scale as the primary explanatory framework. Organised persistence is maintained through coordinated activity extending across multiple spatial and temporal scales simultaneously, from molecular dynamics and physiological regulation to development and evolution. Scale therefore does not describe positions within a hierarchy but the dimensions across which viability-oriented organisation is maintained and transformed. Understanding biological systems requires tracing how organised persistence is coordinated across scales rather than locating causes within discrete levels of organisation.

This article clarifies how APS handles mentalistic language in biology by distinguishing legitimate biological concepts from anthropomorphic projection, and by reframing key terms in viability-oriented, non-mentalistic form.

Biological regulation is one of the most pervasive concepts in biology, yet its meaning often varies across disciplines. In the Agency–Process–Scale (APS) framework, regulation is understood as the coordination of viability-oriented organisation under changing conditions. Living systems remain viable only by maintaining continuity despite continual internal and external change, and regulation is one of the principal organisational processes through which organised persistence is achieved. Rather than serving as biology's ultimate explanatory target, regulation helps explain how living systems preserve viable organisation across multiple scales and timescales.

Biology is often described in terms of hierarchical levels extending from molecules to ecosystems. APS argues that such hierarchies are useful explanatory abstractions but do not accurately describe the organisation of living systems themselves. The article distinguishes epistemic levels, which arise from scientific analysis, from ontological claims about the structure of biological reality. Living systems are not organised into discrete tiers of causal authority but through continuous, scale-coupled, constraint-mediated organisation extending across space and time. Understanding this distinction clarifies why APS rejects hierarchy as an explanatory ontology while retaining hierarchical language as a practical descriptive tool. Biological organisation is better understood through organised persistence, organisational coupling, and constraint relations than through the metaphor of stacked levels.

Agency has re-emerged as a central concept in contemporary theoretical biology. Increasingly, biologists and philosophers argue that living organisms are not passive products of physical processes but active participants in their own persistence, development, and evolution. This article surveys major agency-oriented approaches in contemporary biology, including organism-centred evolution, biological autonomy, developmental agency, and process-based biology. It then explains how the APS framework relates to these approaches while differing from them. APS agrees that agency is fundamental to life, but argues that agency is not merely a property of living systems. Rather, agency is the defining activity through which viability-oriented organised persistence is maintained across time.

Defining life is only part of the scientific challenge. Biology must also determine how living systems are recognised and evaluated in practice. APS distinguishes between definition, diagnosis, and evidence. Life is defined as viability-oriented organised persistence. Diagnosis involves determining whether a system exhibits this organisation. Evidence consists of the observations that support such a judgement. Understanding this distinction clarifies how biology investigates difficult cases ranging from viruses and dormant organisms to possible artificial and origin-of-life systems.

This article explains how scale and time are integrated in APS to produce organised persistence. Living systems do not exist as static entities, but as temporally organised continuity sustained through coordinated activity across interacting spatial and temporal domains. Persistence is therefore understood not as endurance without change, but as the ongoing regeneration of viability-oriented organisation across multiple scales of biological activity.

Living systems persist through multiple, mutually reinforcing forms of continuity. Development preserves continuity through transformation within lifetimes. Ecology preserves continuity through organism–environment coupling. Evolution preserves continuity through historical inheritance across generations. Cognition preserves continuity through evaluation, meaning, and responsiveness to biologically significant conditions. Social organisation preserves continuity through communication, culture, institutions, and coordinated activity. APS interprets these not as separate domains but as complementary continuity architectures that together sustain organised persistence. This article synthesises the major explanatory domains of APS and presents an integrated account of the organisational architecture through which life maintains continuity across scales, contexts, and timescales.

APS approaches biological explanation through continuity structures linking viability, persistence, adaptation, evolution, semiosis, cognition, and consciousness within a unified organisational framework. This article explains how APS organises these continuities and why biological explanation depends upon understanding the transformation of organised persistence across interacting processes, scales, and timescales rather than analysing isolated mechanisms alone.

Theoretical biology and philosophy of biology substantially overlap in subject matter, concepts, methods, and explanatory concerns, making their boundary difficult to locate through disciplinary identity alone. This article develops a comparative account of their division of explanatory labour by classifying epistemic products rather than disciplines, authors, or publication venues. It evaluates six discriminating cases using intended product, evidential responsibility, documented biological consequence, and functional non-redundancy, while retaining uptake, co-production, and null contribution as explicit controls. The comparison distinguishes second-order analysis, clarificatory contribution, ambiguous boundary cases, direct theoretical contribution, co-produced direct contribution, and null direct contribution. The results support a functional and product-relative boundary: philosophical work can contribute directly to theoretical biology when it participates in a biologically answerable explanatory or theoretical product, assumes responsibility to relevant biological evidence, and has documented consequences for biological inquiry. The article does not claim novelty for philosophy-in-science or interdisciplinary co-production; its narrower contribution is a comparative architecture for discriminating among these different forms of explanatory labour.

Living systems do not merely exist through time; they continually organise themselves through time in ways that preserve viability. This article develops an APS interpretation of biological temporality, arguing that continuity, organised persistence, and temporal organisation are fundamental requirements of living systems. Regulation, development, learning, adaptation, ecology, and evolution are interpreted as complementary temporal expressions of viability-oriented organised persistence. Rather than treating time as an external backdrop to biological activity, APS understands temporality as an intrinsic organisational dimension of life and a central component of biological explanation.

Biology explains living systems through multiple successful explanatory approaches directed toward different questions and phenomena. This article asks how those explanatory achievements can be compared without reducing them to a single theory, method, or vocabulary. APS proposes organised persistence—the continuity of living organisation through change—as a candidate comparative target and asks whether comparison through it reveals explanatory relationships, distinctions, or unresolved questions beyond what established explanations already provide.

The search for a fundamental unit of life has shaped biological theory for more than a century. Cells, genes, organisms, species, and ecosystems have each been proposed as biology's primary unit because each explains important aspects of living systems. Yet no single candidate has achieved universal acceptance. In the Agency–Process–Scale (APS) framework, this persistent disagreement reflects a deeper feature of life itself. Living systems are organised through agency, process, and scale rather than around a single privileged entity. Different biological units become important because they illuminate different dimensions of biological organisation. Organisms nevertheless occupy a distinctive explanatory position as regulatory hubs in which genetic, cellular, developmental, ecological, and evolutionary processes become integrated into coherent living activity. The debate over life's fundamental unit therefore reveals less about a missing biological building block than about the inherently multiscale nature of living systems.

The question of life's meaning has traditionally been addressed through religious, philosophical, and existential perspectives. In the Agency–Process–Scale (APS) framework, meaning is understood as a natural feature of living systems rather than an exclusively human concern. Meaning arises wherever conditions, relationships, events, or actions make a difference to the viability, persistence, flourishing, or continuity of living systems. This perspective distinguishes meaning from purpose, function, and goals while explaining how each emerges from biological organisation. Rather than locating meaning outside life, APS interprets meaning as an expression of the organised, agency-driven processes through which living systems maintain continuity across changing conditions. Human meaning represents a particularly reflective and symbolic manifestation of a more general biological phenomenon.

Living systems are composed entirely of physical components and obey the same physical laws as every other system in nature. Yet biology remains a distinct science. Why? APS argues that biology differs from physics not because life violates physical law, but because living systems exhibit viability-oriented organisation. Physics explains the components and processes through which living systems operate. Biology explains how those components are organised to maintain persistence, regulate system–environment relations, and transform through evolutionary time.

Biological agency is not merely a feature of living systems but one of the principal activities through which organised persistence is maintained across changing conditions. APS understands agency as the viability-oriented activity through which living systems regulate, repair, reconstruct, and reorganise themselves in ways that preserve continuity despite ongoing transformation. This article explores the relationship between agency and organised persistence, showing how continuity depends upon active self-maintaining organisation and how agency contributes to development, evaluation, semiosis, ecology, evolution, and diagnosis. Agency is presented not as a specialised cognitive capacity but as a continuity-preserving activity operating across the architecture of life.

APS_PE develops an account of ethics grounded in the biological imperative, arguing that normativity arises from viability-oriented biological organisation and that ethical considerations can be understood as continuous with the processes by which living systems sustain their persistence.

Viruses occupy one of the most debated boundary regions in biology. They evolve, inherit, adapt, and undergo natural selection, yet they do not exhibit the autonomous viability-oriented organisation characteristic of living systems. This article uses viruses as a test case for the APS definition of life, showing why participation in biological processes is not sufficient for biological organisation.

APS interprets biological causation through the viability-oriented modulation of constraints within constraint-closed organisation. Mechanistic interactions remain indispensable and may provide sufficient explanations for many biological questions. Where living organisation and organised persistence are the explanatory targets, APS additionally investigates how materially implemented constraints are maintained, coordinated, and modified across spatial and temporal extents. This organisational account supplements rather than automatically supersedes mechanistic explanation, and its explanatory contribution must be assessed relative to the question being addressed.

Organisms often behave as if they are pursuing goals. They acquire resources, avoid harmful conditions, repair damage, regulate internal states, and reproduce. In APS, this apparent purposefulness is neither an illusion nor evidence of external design. Goal-directed activity emerges because living systems must continually maintain viability in order to persist. This article explains how biological goals arise from viability-oriented organisation and why goal-directedness is a natural consequence of life itself.