Comparative theories reduce to two logical structures at the basic level

Evidence

In a two-level theory, the basic level contains the main causal variables and outcome variable of the theory as a whole. Variables at the basic-level form the building blocks of two-level theories, but there are different logical relationships with which these variables can be put together to form theories. We find that much qualitative and comparative work uses two logical structures at the basic level: (1) a set of causal factors that are individually necessary and jointly sufficient for an outcome; and (2) a set of causal factors that are individually sufficient but not necessary for an outcome. We refer to the first structure as a “conjuncture of necessary causes” to highlight the fact that a combination of necessary conditions are sufficient to produce an outcome. We refer to the second structure using the term “equifinality,” which means that there are various conditions that are sufficient to produce the same outcome and hence multiple paths to the same end (Ragin 1987). For example, a classic example of equifinality is Barrington Moore’s (1966) argument that there are three independent routes to the modern world. — Gary Goertz, Social Science Concepts, 1580

Categorization

• DEFINE: Defines ‘conjuncture of necessary causes’ and ‘equifinality’ as the two basic-level logical structures of two-level theories.
• XREF: Equifinality as ‘multiple paths to the same end’ resonates with ragbroad set-theoretic and process-tracing methodology already familiar from qualitative methods reading.