In real-life management situations, there exist a great deal of fuzziness. In 1965, Zadeh [1] firstly introduced the concept of the fuzzy set, which is an effective tool to deal with fuzziness. However, the fuzzy set employs single index (i.e., membership degree or function) to describe the two states of the support and opposition simultaneously. Namely, if the membership degree of supporting some proposition or phenomena \( x \) is \( \mu (x) \), then the membership degree of opposing the proposition or phenomena \( x \) is just equal to the complement to 1, i.e., \( 1 - \mu (x) \). Hereby, the fuzzy set is no means to describe the neutral state, i.e., neither support nor opposition.