Non-Summative Aggregates
Organizations preserve their identity even when their members change completely.
Summative wholes are exhaustively defined by their parts. Replace any part, you have a different whole. A pile of stones is summative, add or remove a stone, it’s a different pile.
Non-summative aggregates maintain identity despite membership changes. IBM in 2025 contains none of the same people as IBM in 1960, yet it’s still IBM. A university persists through generations of students.
This explains why mereology (the theory of parts and wholes) fails for organizations. If John is “part of” the company, mereology’s transitivity would make John’s eyes part of the company too. That’s clearly wrong.
The persistence mechanism: organizations are sustained by normative structures: documents, roles, obligations, that transcend individual membership. The employment contract creates a position that can be filled by different people over time.
For knowledge systems, this means organizational entities require different modeling patterns than physical objects. You can’t just decompose them into parts.