Secondary-level variables in two-level theories are causes, not mere measures, of the outcome.

Evidence

Considering the explanatory factors in a two-level theory, there are three relationships that can exist between the secondary level and the basic level: causal, ontological, and substitutability. It bears emphasis that none of these relationships is simply one in which the secondary-level variables serve as indicators or measures of the basic-level variables. The role of the secondary-level variables is not to operationalize the basic-level variables. Rather, in a two-level theory, the secondary-level variables always have a causal relationship to the main outcome variable. Two-level theories are complex precisely because the way in which secondary-level variables affect the main outcome varies depending on how they relate to factors at the basic level. — Gary Goertz, Social Science Concepts and Measurement, 1533

Categorization

• DEFINE: Sets out the three relations (causal, ontological, substitutable) that can hold between secondary and basic levels of a two-level theory.
• SEED: Essay angle: why most quantitative work collapses measurement and causation by treating indicators as measures rather than as causal or constitutive parts.