When scholars extend their models and hypotheses to encompass additional cases, they may need to adapt their concepts to fit new contexts. Giovanni Sartori’s work on conceptual traveling and conceptual stretching provides helpful guidance in addressing this fundamental task. Sartori’s framework draws on what may be called a classical understanding of conceptual hierarchies. Each successive concept as one moves down the hierarchy is a “kind of” in relation to the one above it – such that it may be called a kind hierarchy. Concepts have clear boundaries and defining properties shared by all cases deemed to fit the concept. This chapter examines the challenge to this framework presented by two nonclassical approaches: Wittgenstein’s family resemblances and Lakoff’s radial structures. According to these alternative perspectives, concepts may not be sharply bounded, and some attributes may not be shared by all cases viewed as corresponding to the concept. Because they only partly correspond to the concept, this may be called a part–whole hierarchy. With such patterns, strict application of a classical framework can lead to abandoning concepts prematurely or modifying them inappropriately. This chapter discusses solutions to these problems, suggesting that these two forms of hierarchy can productively be used together.

This chapter focuses on one element of causal complexity: disjunctions, or equifinality. Using an example from applied research, it is explained which new SMMR principles and subtypes of cases need to be formulated to capture the consequences for descriptive and causal inference triggered by disjunctions. Learning goals: - Understand the inferential challenges triggered by disjunctions (equifinality) - Get acquainted with the additional sub-types of cases produced by disjunctive solution formulas - Understand how additional principles guide case selection in the presence of disjunctions - Learn if and how moving up the ladder of generality can be used to theorize away disjunctions and the inferential challenges it poses - Become more familiar with the smmr() function and the interpretation of its output in the presence of disjunctions