Parametricity is definitely not impossible to violate, but it's generally morally correct to assume it mostly holds in Haskell. Parametric polymorphism helps ma

Parametricity is definitely not impossible to violate, but it's generally morally correct to assume it mostly holds in Haskell. Parametric polymorphism helps make that workable. Further, type classes help to tag code that does use reflection. You can always get around things, but languages that make a strong commitment to keeping reasoning as a priority are qualitatively different from those that do not.