Necessary-and-sufficient concepts behave cleanly under dichotomous two-valued logic

Evidence

The necessary and sufficient condition structure poses no real problems if one applies two-valued Aristotelian logic with dichotomous variables. Table 2.1 illustrates this with a two-dimensional concept. X1 and X2 are the secondary-level dimensions each of which is necessary. So if X1 or X2 equals zero then so does X (I will use boldface capital characters for basic-level concepts, roman letters for secondary-level dimensions, and italic characters for the indicator/data level). We see sufficiency because when X1 and X2 are present then X has value 1. For example, Przeworski et al. (2000) have a necessary and sufficient condition view of democracy along with dichotomous variables, and everything works as it should. — Gary Goertz, Social Science Concepts, 266

Categorization

• DEFINE: Introduces the notation that distinguishes basic-level concepts (bold capitals), secondary dimensions (roman), and indicator/data level (italics), plus the X1 or X2 = 0 rule.