The weakest-link measure of dyadic democracy is a testable claim about substitutability.

Evidence

After Dixon first proposed the weakest-link idea in 1993, scholars quickly arrived at a consensus that it was the appropriate measure of dyadic democracy. The argument is that the constraints on waging war between two countries are determined by the less democratic of the pair, i.e., the weakest link. The weakest-link measure uses the necessary and sufficient condition concept structure. Each link of the chain is necessary: the strength of one link cannot substitute for the weakness of another. Thus the weakest-link claim can be trans­ lated into one concerning substitutability and concept structure. If the weakest-link hypothesis is correct then the more substitutable the dyadic measure of democracy the less it should be correlated with in­ ternational military conflict. Chapter 5 employs measures of dyadic democracy that vary in their degree of substitutability. It examines whether in statistical fact the weakest link is better than other alterna­ tive concept structures that involve more substitutability, such as the maximum or the mean. — Gary Goertz, Social Science Concepts, 60

Categorization

• DEEPTHINKING: The move from “weakest link is intuitively right” to “weakest link is one point on a substitutability continuum that can be beaten empirically” dissolves a scholarly consensus into a research design.
• SEED: “The weakest link was never tested as a concept structure, only assumed” — an essay on consensus measures that have never been compared against their alternatives.