The first book of its kind, this text explains how all kinds of uncertainties can be handled within the framework of a common theory and set of design tools—fuzzy logic systems—by moving the original fuzzy logic to the next level—type-2 fuzzy logic. It presents a complete development of both type-1 and type-2 fuzzy logic systems, showing how the expanded and richer fuzzy logic contains the original fuzzy logic within it. The text demonstrates, beyond a reasonable doubt, that when uncertainties are present in a problem, much better performance is obtained by using a type-2 fuzzy logic system than by using a type-1 fuzzy logic system.