Lofti Zadeh (1965) devised a form of set theory to model graded categories. He called it fuzzy set theory. In a classical set, everything is either in the set (has membership value 1) or is outside the set (has membership value 0). In a fuzzy set, as Zadeh defined it, additional values are allowed between 0 and 1. This corresponds to Zadeh’s intuition that some men are neither clearly tall nor clearly short, but rather in the middle-tall to some degree.
- Lakoff (1987), Pag. 21