Conceptual Foundations

Biological agency is one of biology's most widely used yet least consistently defined concepts. APS defines biological agency as viability-oriented organisational activity: the present-tense activity through which living systems maintain and re-establish the conditions of their own organised persistence. Agency is therefore distinguished from behaviour, cognition, intention, conscious choice, and attribution based upon hierarchical level. Not every component, subsystem, or organisational extent participating in living activity thereby constitutes an independent agent; agency attribution requires viability-oriented organisation instantiated by the candidate system. Scale addresses the spatial and temporal extent across which persistence relevant to an explanandum is organised rather than identifying levels at which agents occur. Even warranted agency attribution does not guarantee explanatory gain: the explanatory contribution of Agency must be assessed relative to the specified target and strongest relevant comparator. This account establishes Agency as the APS analytic projection concerned with what living systems do while connecting self-maintenance, viability, organised persistence, function, normativity, constraint closure, Process, Scale, and biological explanation.

Persistence is a central explanatory concept within APS because living systems remain continuous despite ongoing material, physiological, developmental, and environmental change. APS treats persistence not as static endurance or material permanence but as organised continuity through transformation. Life itself is defined as viability-oriented, constraint-closed organisation; organised persistence identifies the further explanatory problem of how that organisation maintains and re-establishes the conditions of its continuity through time. Agency, Process, and Scale provide complementary analytic projections through which this problem can be investigated. Organised persistence is therefore a principal APS explanatory target without being the universal explanandum 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 only which properties distinguish living systems, APS investigates the kind of organisation those properties express. Within APS, Life is defined as viability-oriented, constraint-closed organisation, while organised persistence identifies the problem of how that living organisation maintains continuity through change.

This article examines the principle that APS concepts form an organised system of mutually constraining definitions. It explains how conceptual coherence supports interpretative stability, consistency, and controlled theoretical development within APS, while distinguishing these methodological relationships from biological dependencies that require independent justification.

Biological explanation addresses many different explananda and cannot be reduced to a single explanatory target. APS nevertheless identifies organised persistence as a principal explanandum for investigating living organisation: how living systems maintain and re-establish the conditions of their continuity despite continual material, physiological, developmental, ecological, and historical change. APS proposes that life is viability-oriented, constraint-closed organisation and asks how that organisation persists, reorganises, and remains viable through time. This article establishes organised persistence as an explicit APS explanatory target without treating it as the obligatory explanandum of biological explanation generally.

Biological individuality is not adequately explained through static structure, genetic uniqueness, fixed material boundaries, or organismhood alone. Within APS, biological individuals are understood as dynamically stabilised, viability-oriented systems of organised persistence sustained across continual transformation. Individuality emerges through temporal continuity, developmental reconstruction, biological agency, constraint organisation, and organism–environment coupling. APS further distinguishes biological individuality from organismhood, agency, specieshood, and taxonomic classification by grounding individuality in continuity-producing organised persistence. Biological individuals therefore persist not as fixed objects, but as organisational unities enacted across changing conditions, interacting scales, and ongoing processes of transformation.

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. Situated within established research on biological autonomy, organisational closure, regulation, and mechanistic explanation, this perspective identifies relationships relevant to biological continuity without replacing established explanations or claiming distinctive explanatory superiority.

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 accounts of biological organisation. It identifies relations of mutual dependence through which constraints contribute to maintaining the organisation that sustains them. APS treats constraint closure as indispensable to explaining living organisation while distinguishing this contribution from a complete explanation of life. Closure considered abstractly does not by itself establish biological agency, normativity, viability orientation, or organised persistence. These are understood within APS as aspects of one viability-oriented, constraint-closed organisation enacted through time. This article explains what constraint closure contributes to biological explanation, what closure considered in abstraction leaves unexplained, and why its biological significance must be understood within the organisation through which living systems maintain and re-establish the conditions of their own persistence.

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 realised through structures, processes, and activities that make viability-relative contributions within living systems. APS treats Function as a present-tense relation: the contribution a structure, process, or activity makes to the persistence of a viability-oriented, constraint-closed system. This article asks a further organisational question: how are multiple functional contributions coordinated, maintained, and reorganised within the continuing activity through which living systems maintain and re-establish viable organisation? It examines temporal organisation, functional integration, mechanistic realisation, constraint modulation, functional equivalence, adaptive reorganisation, organism–environment relations, and operational persistence. These relations are materially realised and do not constitute separate biological levels or an explanatory domain above mechanism. The article therefore presents function as operational organisation as a bounded, testable explanatory proposal. Whether this organisational analysis provides explanatory gain in any particular case remains explanandum-relative and comparator-relative and requires specification of materially implemented dependencies and empirical support.

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 analytic projection concerned with how living organisation maintains, reorganises, and re-establishes continuity despite change, and situates this account in relation to processual, organisational, and mechanistic approaches to biology.

This article explains Scale in APS as the analytic projection concerned with where persistence is organised across spatial and temporal extents. It distinguishes Scale from physical size, explanatory hierarchy, and materially realised spatial structure while showing why biological explanation must identify the extents across which living organisation is maintained.

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 remain extant but continually maintain and re-establish conditions compatible with their continued functioning across changing circumstances. Within APS, viability identifies these system-relative conditions and the asymmetries they establish between activities that support, undermine, or restore continued functioning. Viability is therefore analytically related to biological agency, organised persistence, function, normativity, development, ecology, and cognition without constituting an intermediate stage through which one becomes another. This article develops viability as an aspect of viability-oriented, constraint-closed living organisation and examines its role in understanding how living systems maintain 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: A Viability-Oriented Framework Integrating Process and Scale,” published in Biological Theory, proposed that biological agency is fundamental to understanding what distinguishes living systems. This article clarifies the continuing significance of that claim within the developed Agency–Process–Scale framework. APS now defines Life as viability-oriented, constraint-closed organisation and biological agency as viability-oriented organisational activity. Agency is therefore not the complete definition of Life, but it can still be described as its defining activity: living organisation is characteristically enacted through activity oriented towards maintaining and re-establishing conditions of viability, while its organised continuity may persist through reversible intervals in which such activity is suspended. This distinction preserves the central insight of the published thesis while separating what Life is from what living systems do and avoiding the treatment of Agency as an additional causal force, a synonym for cognition, or the sole explanation of organised persistence.

Biological agency does not require intention, representation, cognition, deliberation, conscious goals, or other mental states. APS defines biological agency as viability-oriented organisational activity: living systems can act in relation to conditions of their own viability without representing those conditions or intending their own persistence. Viability-relative normativity can therefore structure biological activity without implying mental evaluation, while Biological Evaluation and cognition remain distinguishable from Agency. This article establishes the non-mentalistic boundary of biological Agency while preserving separate criteria for stronger cognitive and mental capacities.

Biology frequently describes living systems through hierarchical levels, from molecules and cells to organisms, populations, and ecosystems. Such representations can be useful for classification, investigation, and communication, but their usefulness does not establish that biological organisation itself consists of discrete causal or ontological levels. APS distinguishes these descriptive partitions from Scale. Scale is the analytic projection concerned with where persistence is organised across spatial and temporal extents. It does not replace levels with another biological hierarchy, nor does it imply that living systems must always be explained across multiple scales. The explanatory task is to identify the materially realised processes, constraints, interactions, and dependencies relevant to a biological target and to determine the spatial and temporal extent across which they must be considered.

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.

This article clarifies the roles of space and time in biological explanation within the APS framework. It argues that space and time are not primary explanatory domains in biology but are organisational dimensions through which viability-oriented processes are structured and understood. By situating spatial configuration and temporal extension within the dynamics of organisation, the analysis shows how biological systems are best understood as processual, scale-dependent, and structured by constraints that sustain viability rather than by static spatial form or linear temporal sequence.

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 through hierarchical levels extending from molecules to ecosystems. Such representations can be useful for investigation, modelling, communication, and teaching, and some can track materially real part–whole or nested relations. Neither fact establishes that living organisation forms a universal hierarchy of discrete causal or explanatory levels. APS therefore does not replace hierarchy with interacting scales. It asks which materially realised processes, constraints, interactions, structures, and organisational relations are relevant to the explanandum. Scale then identifies the spatial and temporal extent across which the persistence relevant to that explanandum is organised. APS thus replaces the presumption of hierarchical ontology with analysis of organisation, while retaining hierarchical descriptions where they serve a legitimate explanatory purpose.

Agency has become increasingly prominent across contemporary theoretical biology, but shared agency-related vocabulary does not establish a unified explanatory tradition. Organism-centred evolution, biological autonomy, organismic biology, developmental plasticity, evolutionary developmental biology, and process biology differ in their explanatory targets, criteria for agency attribution, causal commitments, and intended explanatory contributions. APS compares these approaches target by target rather than treating conceptual convergence as explanatory equivalence. Biological agency is viability-oriented organisational activity, but warranted agency attribution does not by itself establish explanatory gain. The contribution of Agency must therefore be assessed relative to a specified explanandum and the strongest relevant comparator.

This article clarifies evaluation within the Agency–Process–Scale (APS) framework. Evaluation is understood as the differential modulation of activity relative to conditions of viability. Living systems do not merely undergo physical processes; they regulate activity in relation to conditions that support or undermine persistence. Evaluation therefore constitutes the real-time enactment of biological normativity and provides the organisational bridge linking viability, semiosis, meaning, cognition, temporality, and biological agency.

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 temporal continuity and Scale contribute to the APS account of organised persistence. Living systems persist through materially realised organisation that is continually maintained and re-established through change. That organisation extends across spatial and temporal extents appropriate to the biological processes being explained. Time makes the continuity of living organisation explicit; Scale identifies where that persistence is organised across spatial and temporal extents. Neither is an independently acting cause or component of life. Together they provide complementary explanatory perspectives on the organised continuity through which living systems persist.

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 and organised persistence are analytically distinguishable aspects of one living organisation rather than successive stages in a causal sequence. Agency identifies viability-oriented organisational activity in the present, while organised persistence identifies the continuity of living organisation through change. Activities analysed under Agency can contribute materially to maintaining and re-establishing the conditions of that continuity through regulation, repair, compensation, reconstruction, and reorganisation without Agency becoming an independent cause or sufficient explanation of persistence. This article develops that relationship while preserving the distinction between explanatory target, analytic projection, materially realised activity, and demonstrated explanatory gain.

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.

In APS, biological individuality is understood as a dynamically maintained continuity of viability-oriented organisation rather than a fixed material substance or static structural entity. Organisms persist through regulated transformation, repair, ecological coupling, developmental integration, and continuity-preserving organisation across time. APS therefore interprets individuality as processual: not because organisms are vague or unreal, but because biological identity is constituted through organised persistence rather than immutable material sameness. This article introduces the APS processual account of individuality and situates it within the broader continuity architecture developed further in *Biological Individuality — Organised Persistence Through Time*.

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.