[Haskell-cafe] Why no IO transformer monad?

[Henning Sato von Rosen]

Hi all!

For each basic monad there seems to be a corresponding transformer,
e.g.  'StateT' for 'State' and so on.

I guess the reason lies in the fact that if there were an IO
Transformer monad, one might run it and get the 'Universe' out of the
IO monad.

But, I am working on understanding IO magic, on a much more concrete
level, so I am am looking for a really good explanation of the above.
(And the IO monad in general.)

Thanks!

/Henning