Biological systems are often described using hierarchical language:
- lower and higher levels
- simple and complex forms
- or upward-building layers of organisation
APS treats such descriptions primarily as explanatory conveniences rather than as literal features of biological reality.
In place of hierarchy, APS uses the concept of scale.
Living systems are organised across continuously interacting spatial and temporal scales, linked through processes of scale-coupling and reciprocal organisational dependence. Molecular, physiological, behavioural, ecological, and evolutionary processes are not separate ontological layers but dynamically integrated aspects of continuous biological organisation.
APS therefore rejects the idea that biological explanation must proceed:
- from lower to higher levels
- from more fundamental to less fundamental domains
- or through unidirectional chains of causation
Instead, biological organisation is understood through reciprocal relations distributed across interacting scales.
APS also distinguishes scale from resolution.
Scale refers to the spatiotemporal organisation of biological activity itself. Resolution refers to the granularity at which that organisation is described or analysed. What appear as “levels” often reflect differences in explanatory resolution rather than discrete layers of reality.
This shift matters because hierarchical language can unintentionally imply:
- privileged explanatory domains
- ontological stratification
- or one-way causal determination
APS instead understands living systems as dynamically organised, scale-coupled processes sustained through reciprocal organisational relations.
Key Point. Biological organisation varies across interacting scales, not through ranked ontological levels or hierarchical layers of reality.