[Haskell-cafe] monoids and monads

Hello, I was wondering today, is this generally true? instance (Monad m, Monoid a) => Monoid (m a) where mempty = return mempty mappend = liftM2 mappend I know it isn't a good idea to use this instance, but assuming that the instance head does what I mean, is it valid? Or more generally is it true for applicative functors as well? I think it works for a few tricky monads, but that's not any sort of proof. I don't even know how to express what would need to be proven here. Any resources for how I could develop a means to reason about this sort of property? Thanks, John