[Haskell-cafe] Either e Monad

Dear all, Where is the Monad instance declaration of Either e?

From the description of Control.Monad.Error, I deduce that Either e is an instance of Monad.

http://haskell.org/ghc/docs/latest/html/libraries/mtl/Control-Monad-Error.ht... class Monad m => MonadError e m | m -> e where ... Error e => MonadError e (Either e) But, I cannot find the Monad instance declaration of Either anywhere. Thanks. -- Deokhwan Kim