Weakest-link aggregation is itself a causal theory about how democracy prevents war.

Evidence

This embedded hypothesis is assumed when the measure is used to test the democratic peace with basic-level variables. The standard basic-level hypothesis is between a military conflict dependent variable (e.g., militarized disputes or crises) and a dyadic democracy independent variable. The weakest link is used to make up that basic-level, dyadic democracy independent variable which is then correlated with the dependent conflict variable. — Gary Goertz, Social Science Concepts, 62

Categorization

• DEFINE: Explains the weakest-link aggregation rule for a dyadic democracy score — the whole is only as democratic as its least democratic member.
• QUESTION: If weakest-link is a theory, why do most democratic-peace tests treat the resulting score as a neutral measurement of regime type?