APS — A Viability-Oriented Framework for Understanding Life

APS (Agency–Process–Scale) is a conceptual framework for understanding life as viability-oriented, constraint-closed organisation. It does not begin from components such as genes, molecules, or traits, but from the organisation through which living systems sustain their own existence over time.

At its core, APS proposes that biological explanation requires an integrated account of agency, process, and scale. These are not separate levels or distinct sources of causation, but co-constitutive dimensions of living systems.

biological agency refers to the viability-oriented activity through which systems regulate and sustain themselves
process describes the dynamic organisation through which this activity unfolds
scale captures the spatial and temporal extent across which organisation is coordinated

Together, these dimensions form an explanatory grammar: a structured way of identifying what counts as a cause, a unit, and an explanation in biology.

APS Box — How APS Definitions Work

APS definitions do not function independently. Each concept derives its meaning from its role within a unified explanatory system.

Terms such as agency, process, and scale are not isolated descriptors but co-constitutive aspects of viability-oriented, constraint-closed organisation. Their definitions are therefore relational: each term is understood through its connections to others and through the role it plays in explaining how living systems sustain and transform their persistence.

This approach differs from traditional dictionary-style definitions, which treat concepts as self-contained. In APS, definitions operate as part of an explanatory grammar: they clarify how concepts function together to make biological organisation intelligible.

Key Point. APS definitions are relational and system-dependent: each term gains meaning from its role within the explanatory structure of the framework.

Life as Viability-Oriented Organisation

In APS, life is not defined by a list of properties or components, but by a specific form of organisation. A system is living if it exhibits viability—the capacity to sustain the conditions of its own persistence—through internally generated activity.

This requires constraint closure: a network of processes in which the constraints that enable activity are themselves maintained by that activity. Such systems do not merely undergo change; they actively regulate and reorganise themselves in response to perturbation. Because their organisation must be continuously maintained, changes are not neutral but evaluated in relation to viability.

This organisation gives rise to normativity. For a living system, some states and changes matter because they affect its continued existence. Normativity is therefore not imposed from outside or inferred by an observer, but arises from the system’s own viability conditions.

APS Box — What APS Does Not Assume

APS introduces a specific explanatory grammar for biology. It does not rely on a number of common assumptions that are often taken for granted in other frameworks.

No reduction to parts as primary explanans
APS does not assume that biological explanation is fundamentally about decomposing systems into constituent parts.
No primacy of genetic or informational code
Genes and information are treated as components within organised systems, not as the defining basis of life.
No hierarchy of fixed levels of organisation
APS does not assume discrete levels (e.g. gene → cell → organism) as ontological layers; it works with continuous, interacting scales.
No requirement for representation or internal models
Basic biological regulation does not depend on representational content; viability-oriented modulation precedes representation.
No external assignment of function or purpose
Function and purpose are not imposed by observers but arise from the organisation of viability-oriented activity.
No separation between organism and environment as independent systems
Organism and environment are understood as dynamically coupled aspects of a single viability-oriented process.
No assumption that normativity is mental or subjective
Biological normativity is enacted through organisation and does not depend on consciousness or experience.

APS does not reject these concepts outright, but reinterprets them within a framework grounded in viability-oriented, constraint-closed organisation.

Key Point. APS reframes common biological assumptions within a viability-oriented, constraint-closed framework rather than accepting them as explanatory primitives.

From Components to Organisation

Traditional approaches in biology often prioritise components—genes, molecules, or traits—as primary explanatory units. APS does not reject these, but repositions them within an organisational framework.

Components matter insofar as they contribute to the maintenance of the system’s viability. Their roles are defined not in isolation, but by how they participate in constraint-closed organisation.

This shift changes what counts as explanation. Rather than asking how components produce outcomes, APS asks how systems sustain themselves through coordinated organisation across scales.

APS Box — Why APS Is Not Arbitrary

The Agency–Process–Scale (APS) framework does not introduce an arbitrary set of categories. It identifies the minimal explanatory structure required to account for viability-oriented, constraint-closed organisation.

Agency, process, and scale are not convenient descriptors but necessary dimensions of biological explanation. Without agency, biological normativity disappears and no distinction can be made between persistence and failure. Without process, organisation becomes static and cannot account for ongoing maintenance. Without scale, coordination across spatial and temporal domains cannot be explained.

Any framework that adequately explains living systems must therefore include these dimensions, even if under different terminology.

Key Point. APS is not one framework among many—it makes explicit the conditions required for biological explanation to remain coherent.

Explanation Without Hierarchy

APS replaces the idea of fixed “levels of organisation” with multi-scale, processual organisation. Biological systems are not structured as hierarchies of discrete levels, but as dynamically coupled processes operating across overlapping scales.

Causation in biology is therefore not located at a privileged level. Instead, agency, process, and scale are co-constitutive, continuously shaping, enabling, and constraining one another.

This allows APS to integrate within a single explanatory framework:

molecular processes
physiological regulation
organism–environment interactions
ecological and evolutionary dynamics

within a single explanatory framework.

APS Box — Hierarchy vs Scale

Biological systems are often described using hierarchical language: lower and higher levels, more basic and more advanced forms, or processes that build upward from simple to complex.

APS treats this as a modelling convenience, not a feature of reality.

In place of hierarchy, APS uses the concept of scale. Biological organisation unfolds across continuous, interacting spatial and temporal scales, with no intrinsic ranking of “higher” or “lower.” What appear as levels are regions of relative stability within a dynamically coupled system.

This shift matters because hierarchical language can imply that some processes are more fundamental than others, or that explanation proceeds in a single direction. APS instead emphasises reciprocal, scale-coupled organisation, where causation and regulation operate across interacting domains.

Key Point. Biological organisation varies in form across scales, not in rank within a hierarchy.

From Persistence to Evolution

APS distinguishes between the ongoing maintenance of life and its long-term transformation.

persistence refers to the present-tense maintenance of viability
evolution describes the long-term transformation of this organisation across generations

Natural selection operates only within systems capable of sustaining organised persistence. Evolution is therefore not prior to life, but depends on the existence of viability-oriented organisation.

A Framework for Biology

APS does not replace existing biological theories but provides a framework for integrating them. It clarifies how different approaches—molecular biology, physiology, ecology, and evolution—relate to one another by situating them within a shared explanatory grammar.

It also provides a basis for distinguishing living systems from non-living ones, for analysing borderline cases, and for extending biological concepts such as agency, cognition, and function beyond traditional boundaries.

For a concise overview, see What Is APS? — A One-Page Framework Overview.
For a structural account of the framework, see Understanding APS — The Structure of the Framework.
For the definition of life, see What Is Life?.

Key Points

APS defines life as viability-oriented, constraint-closed organisation
Biological explanation requires integrating agency, process, and scale
These dimensions are co-constitutive, not hierarchical
Normativity arises from the organisation required for persistence
Evolution depends on the prior existence of organised persistence