Concept formation is critical for many social scientific goals, yet it often appears neglected. This chapter underscores the importance of concepts in empirical work oriented toward causal inference, including experiments. It explores the role of conceptual hierarchies, typologies, and dichotomies both for causal attribution and for assessing generalizability. Using an example from the Metaketa Initiative, this chapter highlights the value of Sartori’s ladder of abstraction for fostering cumulative learning from experimental research. Wider use of the tools of concept formation can aid assessment of both the internal and external validity of causal claims.

David Collier and Steven Levitsky’s original “Democracy with Adjectives” article (1997) offered a useful corrective to Sartorian thinking about conceptualization, and the new revised version further clarifies its contribution. There is a crucial difference between identifying a diminished subtype (moving from democracy as attributes “A and B and C” to “A and B and not C”) and moving up the ladder of abstraction (from democracy as attributes “A and B and C” to “A and B and either C or not C”). Diminished subtypes are more precise and do not necessarily increase the extension of a concept. This chapter offers a critique of both examples of conceptual innovation, which are grounded in categorical thinking, from the conceptual approach used by the Varieties of Democracy (V-Dem) project, which conceives of democracy as an aggregate of multiple continuous dimensions. Examples using V-Dem data suggest that it is possible to create measurements of specific concepts that are both qualitatively rich and quantitatively precise. However, the measurement of very general concepts such as democracy comes at the cost of some quantitative information and conceptual clarity.