Conventional Framing
Persistence ordinarily means continuity through time. Something persists when it continues rather than ceasing to exist, disintegrating, or losing the continuity relevant to the question being asked.
In biology and ecology, persistence may refer to different forms of continuity, including survival, lineage continuity, population persistence, ecological stability, or the maintenance of biological organisation. These usages should not automatically be treated as equivalent. What persists, over what interval, and according to what criterion depend on the explanandum.
APS therefore retains persistence as a general concept rather than defining it as a distinct biological activity.
Persistence in Living Systems
Persistence becomes a distinctive explanatory problem in living systems because biological continuity does not normally depend upon material invariance.
Living systems undergo continual change. Molecules are replaced, structures are repaired or remodelled, physiological states fluctuate, development alters form, behaviour changes relations with surrounding conditions, and environmental circumstances vary. Yet living organisation can remain continuous through these transformations.
Persistence in this context identifies the continuity requiring explanation. It does not by itself explain how that continuity is maintained.
This distinction is important. APS does not define persistence as the activity through which a living system maintains itself. Biological agency identifies viability-oriented organisational activity. Process asks how organisational continuity is maintained through change. Persistence identifies the continuity to which those explanatory questions are directed.
Persistence and Organised Persistence
APS distinguishes persistence from organised persistence.
Persistence is continuity through time.
Organised persistence is the continuity of living organisation through change.
The second concept is therefore more specific. A non-living object may persist through relative material stability. A living system typically persists while undergoing extensive material and functional change. What remains continuous is not necessarily its constituent matter or an unchanging structure, but its living organisation.
Organised persistence identifies this specifically biological form of continuity.
Persistence and Life
Persistence should not be confused with the APS definition of Life.
APS defines Life as viability-oriented, constraint-closed organisation.
Persistence does not define that organisation. Nor does the fact that something persists establish that it is alive. Many non-living objects, structures, patterns, and systems can persist.
For living systems, the relevant question is how viability-oriented, constraint-closed organisation maintains continuity despite the changes through which it is materially realised. APS uses organised persistence to identify that continuity.
Life and persistence are therefore related without being synonymous:
- Life identifies the organisation characteristic of living systems.
- Persistence identifies continuity through time.
- Organised persistence identifies continuity of living organisation through change.
Persistence and Viability
Persistence and viability are also distinct.
Viability concerns the conditions under which living organisation can continue to function. Some conditions support continued functioning, while others impair or terminate it.
Persistence concerns continuity through time.
A living system persists only while the relevant continuity is maintained, but persistence should not therefore be defined as viability-oriented activity. Viability specifies conditions relevant to continuation; persistence identifies the continuation itself.
This distinction prevents the concepts from becoming circular. Viability is not defined merely as whatever produces persistence, and persistence is not defined merely as whatever maintains viability.
Persistence, Process, and Scale
Persistence is especially important to the Process and Scale projections of APS.
Process asks:
How is organisational continuity maintained through change?
Persistence supplies the continuity whose maintenance Process investigates.
Scale asks:
Across what spatial and temporal extents is persistence organised?
The answer depends on the biological question. Relevant organisation may need to be traced across molecular, cellular, organismal, environmental, developmental, intergenerational, or other spatial and temporal extents.
These extents do not constitute a predetermined explanatory hierarchy. They identify where the relations relevant to a particular explanandum must be investigated.
Persistence and Evolution
Persistence and evolution concern different temporal questions.
Persistence concerns continuity through time. Evolution concerns the historical transformation of living organisation across generations.
Evolutionary change can alter the forms of organisation through which living systems maintain continuity, but evolution should not be defined simply as the transformation of persistence. Established evolutionary mechanisms and processes explain historical biological change; APS asks how those changes bear upon living organisation and the ways in which its continuity is maintained.
Key Point
Persistence is continuity through time. In APS, it identifies a phenomenon requiring explanation rather than the activity that explains it. When the continuity at issue is specifically the continuity of living organisation through change, APS calls it organised persistence.