Each single necessary condition is insufficient, but their joint presence produces the outcome.

Evidence

An excellent example of a two-level theory that uses a substitutable relationship between the secondary and the basic levels is the work of Ostrom (1991). Ostrom identifies eight conditions4 that are necessary for her key outcome of “institutional functioning.” Of these eight conditions, monitoring and sanctions stand out. In her American Political Science Association presidential address, she selects them for special attention: “Most robust and long-lasting common-pool regimes involve clear mechanisms for monitoring rule conformance and graduated sanctions for enforcing compliance” (Ostrom 1997, 8). Thus, her argument emphasizes necessary conditions that form a conjuncture that is sufficient. — Gary Goertz, Social Science Concepts and Measurement, 1571

Categorization

• XREF: Connects to the Milgrom law-merchant material: information/monitoring institutions as the load-bearing variable in sustaining cooperation.
• DEFINE: Names the conjuncture structure: individually necessary conditions that are jointly sufficient.