Observable features such as movement, growth, replication, or response to stimuli are often taken as evidence of life. However, these features can occur in non-living systems.
The key question is not whether a system behaves, but whether its activity is organised to sustain its own viability.
| Observable Feature | APS Interpretation |
|---|---|
| Movement | Is movement regulated for persistence? |
| Growth | Is growth constraint-regulated and self-maintaining? |
| Replication | Is replication embedded in self-sustaining organisation? |
| Adaptation | Does adaptation restore viability conditions? |
Key Point:
Behaviour becomes biological evidence only when it reflects self-maintaining, viability-oriented organisation.