In section 5 of _Fun with Phantom Types_, Hinze states... "Let us move on to one of the miracles of theoretical computer science. In Haskell, one cannot show values of functional types. For reasons of computability, there is no systematic way of showing functions and any ad-hoc approach would destroy referential transparency (except if show were a constant function). For instance, if show yielded the text of a function definition, we could distinguish, say, quick sort from merge sort. Substituting one for the other could then possibly change the meaning of a program." ...I guess I'm not understanding what that means. Would there be some sort of contradiction that arises when trying to evaluate "show (show)" or somesuch? Can anyone point me in the direction of information that tries to explain why this is? I'm at a loss as to what search terms to use. Thanks, Greg Buchholz