Boundary
The demarcation separating a system from its environment. Not merely a line, but a structured interface where exchanges occur and identity is maintained.
Formal Definitions
Mobus & Kalton (2015):
“The boundary B at level l is a tuple: B_{i,l} = ⟨P, I⟩ where P is the set of properties and I is the set of interfaces.”
(Principles of Systems Science, Section 4.3)
Boundedness appears as a core ontological element at Level 0 in Mobus’s systems ontology, alongside SYSTEM, PROCESS, and BEHAVIOR.
(Section 3.5, Fig. 3.13)
Bunge (1979): Bunge treats boundary implicitly through the formal requirement that composition (C) and environment (E) be mutually disjoint sets: C ∩ E = ∅. The boundary emerges from this separation rather than being defined independently.
(A World of Systems, Chapter 1)
Synthesis
Mobus makes boundary explicit as a composite of properties (what the boundary IS) and interfaces (where exchanges HAPPEN). Bunge’s implicit treatment emphasizes that boundary is a logical consequence of distinguishing system from environment. Both agree boundary placement is an analytical choice — the same phenomenon can be bounded differently depending on the question being asked.
Key Insight
Boundaries are not passive containers but active regulators. They determine what flows in and out, maintaining system identity while permitting necessary exchanges with the environment.
Explore Further
- Explaining behavior requires complete circuits — Bateson on boundaries defined by causal loops
- Mind extends beyond the body — Radical reconception of mental boundaries
- Self as part of larger system — Boundary between self and environment dissolves
- Integration vs disintegration — Boundaries defined by cohesion gradients
Related Concepts
- System — what the boundary encloses
- Environment — what lies outside