Many discussions of life move directly from recognising living systems to proposing definitions of life. APS argues that these are distinct scientific tasks and that confusion between them has contributed to the persistence of the question What is life?
Recognition asks whether a system exhibits characteristics commonly associated with living systems. Metabolism, regulation, growth, reproduction, responsiveness, and adaptation may all provide important evidence that a system is living.
Definition asks what qualifies a system as living. It seeks to identify the organisational conditions that distinguish living systems from other organised systems.
Explanation asks a different question again. Rather than identifying living systems or defining their characteristics, it asks what kind of organisation makes those characteristics possible as coordinated expressions of a single biological phenomenon.
APS therefore distinguishes three complementary questions:
- Recognition: Does this system exhibit the characteristics of life?
- Definition: What qualifies a system as living?
- Explanation: What organisation makes living systems possible?
The primary concern of APS is explanation. It investigates the organisation through which metabolism, development, regulation, function, reproduction, evolution, and other biological phenomena become integrated expressions of living systems.
Key Point: Recognising life, defining life, and explaining life are related but distinct scientific tasks. APS is principally concerned with explaining the organisation that makes living systems possible.