I agree that Haskellers tend to get ridiculously over-excited about category theory, but it's simply not true that there's only "one category in play". Categor

I agree that Haskellers tend to get ridiculously over-excited about category theory, but it's simply not true that there's only "one category in play". Categories abound in Haskell, for example the Kleisli category, and any instance of Category that isn't (->).