The adverb is not your friend

"Consider the sentence He closed the door firmly. It's by no means a terrible sentence (at least it's got an active verb going for it), but ask yourself if firmly really has to be there. You can argue that it expresses a degree of difference between He closed the door and He slammed the door, and you'll get no argument from me ... but what about context? What about all the enlightening (not to say emotionally moving) prose which came before He closed the door firmly? Shouldn't this tell us how he closed the door? And if the foregoing prose does tell us, isn't firmly an extra word? Isn't it redundant?" (#2 p.118)