What Does Biology Explain?
Biology is often described as the science of life. But this leaves open a deeper question: what does biological explanation actually explain?
Standard answers point to mechanisms, components, or processes. Biology explains how genes are expressed, how metabolic pathways operate, how organisms develop, and how populations evolve. These explanations have achieved extraordinary success.
Yet they often proceed without specifying what makes their subject matter distinctively biological. They describe how systems behave, but not what makes those systems living.
The central question is therefore not only how biological systems work, but what kind of biological organisation must be in place for such explanations to be meaningful.
For a guided entry into how APS develops biological explanation, see:
→ How APS Explains Life — A Two-Step Guide
Mechanism and Its Limits
Much of modern biology is organised around mechanistic explanation.
Mechanistic accounts identify parts, specify their interactions, and show how these interactions produce observable outcomes. This approach has been highly productive, especially in molecular and cellular biology.
However, mechanism alone does not explain why a system is a living system rather than a complex physical arrangement.
A mechanism can operate without sustaining itself. It can produce outputs without maintaining the conditions required for its own continued operation. In such cases, the system remains externally grounded: its persistence depends on conditions imposed from outside.
Living systems differ in a crucial respect. Their biological organisation is such that the processes they enact contribute to the maintenance of the conditions that allow those processes to continue.
Mechanistic description captures how processes unfold. It does not, by itself, explain why those processes are organised in a way that sustains the system as a living whole.
From Description to Explanation
This distinction reveals a deeper issue.
Descriptions catalogue what happens. Explanations account for why it happens in a way that is characteristic of the system under study.
In biology, description often precedes explanation. We identify structures, trace pathways, and measure changes. But without a clear account of what makes these processes biologically organised, such descriptions risk remaining incomplete.
A fully biological explanation must therefore do more than specify mechanisms. It must account for the biological organisation that makes those mechanisms part of a living system.
Viability-Oriented Organisation as the Explanatory Target
The APS framework clarifies this target.
Living systems are organised around maintaining their own viability. Their processes are not simply coordinated; they are oriented toward sustaining the conditions of their continued existence.
This biological organisation is constraint-closed: the processes of the system contribute to maintaining the constraints that enable those very processes to occur.
Biological explanation must therefore account for this form of biological organisation. It must explain how a system’s activity contributes to its own persistence, and how this contribution is maintained under changing conditions.
Without this, explanations remain partial. They describe what happens, but not what makes those processes biologically meaningful.
Agency and Normativity in Explanation
Once viability-oriented biological organisation is recognised, further features of biological systems become intelligible.
Living systems exhibit biological agency: their activity is organised around sustaining themselves. This introduces a form of normativity.
Some states support persistence; others undermine it. This distinction is not imposed from outside but arises within the biological organisation of the system itself.
As a result, biological explanations routinely invoke notions such as function, regulation, success, failure, and malfunction. These are not metaphorical. They reflect real features of systems whose activity is oriented toward continued viability.
To explain a biological process is therefore to explain how it contributes—successfully or unsuccessfully—to the persistence of the system.
Process and Scale in Biological Explanation
Biological organisation is inherently processual and multi-scale.
Processes occur across a wide range of temporal and spatial scales: molecular reactions, cellular regulation, organismal development, and evolutionary change. These processes are not independent. They are coupled in ways that allow the system to persist despite continual change.
Explanation must therefore track not only individual mechanisms, but the coordination of processes across scales.
Short-term regulation and long-term evolution are not separate domains. They are different temporal expressions of the same viability-oriented biological organisation.
APS provides a framework in which these relations can be understood as aspects of a single explanatory structure.
Beyond Gene-Centric and Trait-Based Accounts
Many explanatory frameworks in biology focus on genes, traits, or population-level patterns.
These approaches provide powerful tools for modelling and prediction. However, they often treat the living system as a passive substrate on which processes operate.
In contrast, APS emphasises that genes, traits, and populations are components or descriptions of systems that must already be organised to persist.
Natural selection, for example, explains changes in populations over time. But it presupposes systems capable of maintaining organised persistence across generations.
Biological explanation must therefore include the conditions that make such processes possible, not only the processes themselves.
Explanatory Adequacy in Biology
What, then, counts as an adequate biological explanation?
An explanation is biologically adequate when it accounts for:
- how a system maintains its own viability
- how its processes contribute to that maintenance
- how this biological organisation is sustained across scales and over time
Explanations that omit these features may still be useful, but they remain incomplete from a biological perspective.
APS does not replace existing explanatory approaches. It clarifies the conditions under which those approaches become fully biological.
Why This Matters
Clarifying the target of biological explanation has practical and conceptual consequences.
It explains why concepts such as function and regulation are indispensable. It grounds evolutionary theory in the activity of living systems. It provides criteria for identifying life in borderline or synthetic cases. It clarifies the continuity between biological and cognitive processes.
Most importantly, it makes explicit the organisational conditions that biological explanations already rely on when they succeed.
To specify what biological explanation must explain, however, is only the first step. Once viability-oriented, constraint-closed organisation is identified as the explanatory target, a further question arises: how must explanation be structured to account for it? This question is addressed in The Structure of Biological Explanation in APS, which develops the explanatory grammar required to integrate agency, process, scale, and temporal dynamics within a unified framework.
Conclusion
Biology does not simply describe complex systems. It explains systems that sustain themselves.
The APS framework identifies viability-oriented, constraint-closed biological organisation as the defining feature of such systems. Biological explanation is therefore the explanation of how this biological organisation is established, maintained, and transformed.
By clarifying what needs to be explained, APS establishes the target of biological explanation and prepares the ground for specifying the structure required to explain it.