Warren, McCain, and Obama Needed Fuzzy Sets at Presidential Forum

During a presidential forum in the 2008 US presidential campaign, the moderator, Pastor Rick Warren, wanted Senator John McCain and then-Senator Barack Obama to define rich with a specific number. Warren wanted to know at what specific income level a person goes from being not rich to rich. The problem with this question is that there is no specific income at which a person makes the leap from being not rich to being rich. This is because rich is a fuzzy set, not a crisp set, with different incomes having different degrees of membership in the rich fuzzy set. Fuzzy logic is needed to properly ask and answer Warren's question about quantitatively defining rich. An imprecise natural language word like rich should be considered to have qualitative definitions, crisp quantitative definitions, and fuzzy quantitative definitions.