Being a member state of the European Union is necessary for having the Euro as the official currency: the set of EU member states is a superset of the set of countries with the Euro as a national currency. Generally, if a condition X is necessary for an outcome Y, then X is a superset of Y. In this chapter, we introduce the notion of necessity and discuss the analysis of necessary conditions in R. We explain what necessity is, how to analyze and visualize necessary conditions, how to interpret the results, and how to avoid common pitfalls. We outline the basic protocol for the analysis of necessity in R, both for the analysis of individual necessary conditions and for conditions combined with a logical OR, that is necessary disjunctions composed of so-called SUIN conditions.

Learning goals:

- Understanding of the basic logic of necessity.

- Familiarity with different approaches to analyzing necessity in QCA and the protocol for the analysis of necessity.

- Basic understanding of possible analytic pitfalls when analyzing necessity and ways of avoiding them.

- Ability to implement an analysis of necessity in R and visualize the results.