CLOS only allows dispatch on classes and not types, because there is no hierarchy in types. For example, if you have a method specializing on the type (satisfi

CLOS only allows dispatch on classes and not types, because there is no hierarchy in types. For example, if you have a method specializing on the type (satisfies a) and a method specializing on the type (satisfies b), and you call a generic function with an object that satisfies both a and b, which method should be called first? Or methods specializing on the types (integer 0 8) and (integer 1 9). If the argument is 5, which type is more specific? Classes are a subset of types with a certain hierarchy, so there is always a "correct" order for methods to be called in.