I agree with what you’re saying, but I think calling them “special cases” takes away from the elegance of the system. Haskell users frequently say things like “

I agree with what you’re saying, but I think calling them “special cases” takes away from the elegance of the system. Haskell users frequently say things like “the IO monad” or “the list monad”, but probably the more accurate way would be to say the “the monad instance of IO”. Monad is a typeclass (analogous to an interface in OOP or traits in Rust). IO is a type. To make some type a member of monad (or any other typeclass), you just need to write the required functions in an instance declaration. You can make a type a member of as many typeclasses as you want. List is a member of Foldable, Monad, etc. Calling that a special isn’t quite right as it is very common for a type to be a member of many typeclasses. You’re entirely correct in saying the Monad typeclass offers no way to extract values. But there actually is an extract function called unsafePerformIO with type “IO a -> a”. The name says it all: use it and you’ll lose all of the safety normally afforded by keeping data derived from effects inside the IO type.