APS distinguishes between diagnosis and biosignatures.
Both concern evidence for life, but they operate differently.
Diagnosis evaluates biological organisation directly.
It typically involves:
- perturbation,
- organisational response,
- endogenous restoration,
- and assessment of viability-oriented regulation.
Diagnosis therefore tests whether a system actively sustains the conditions of its own persistence.
Biosignatures, by contrast, provide indirect evidence.
They are observational indicators that may suggest the presence of viability-oriented organisation when direct intervention is impossible.
Examples include:
- atmospheric disequilibrium,
- persistence far from equilibrium,
- regulated energy flow,
- recovery patterns,
- or coordinated multiscale activity.
APS therefore distinguishes:
| Diagnosis | Biosignatures |
|---|---|
| Direct evaluation | Indirect inference |
| Perturbational | Observational |
| Tests organisation | Infers organisation |
| Stronger evidence | More uncertain |
Biosignatures do not define life. They provide evidence that organised, self-maintaining activity may be present.
Key Point: APS diagnosis evaluates biological organisation directly where possible; biosignatures infer it indirectly from observable patterns of organised persistence.