Hello All, Why does this compile class Special a where isSpecial :: a -> Bool whereas, GHC 7.6 complains about this class AlsoSpecial a where isAlsoSpecial :: b -> Bool This is the error message I get: The class method `isAlsoSpecial' mentions none of the type variables of the class AlsoSpecial a When checking the class method: isAlsoSpecial :: forall b. b -> Bool In the class declaration for `AlsoSpecial' My question is: Why must I use the type variable of the class declaration (i.e. *a*) in the type signature for the associated method? Is there a fundamental reason for this or is it just a GHC specific limitation? I didn't see a need for it when watching this video http://channel9.msdn.com/posts/MDCC-TechTalk-Classes-Jim-but-not-as-we-know-... that explains the translation that GHC does to turn type classes into core. Thanks! Dimitri