On Feeling Bad and Badly

"Clearly I'm interrupting; I feel badly. Let me ... what are you drinking? I'll buy y..."
"Bad."
"Bad? Sorry, I feel...?"
"You feel bad. Badly is an adverb, so to say you feel badly is to say that the mechanism which allows you to feel is broken."

(From the movie Kiss Kiss Bang Bang)

Thomas Presskorn draws attention to the difference between adjectives and adverbs in his comment to my post on vanity and doing things badly. (We owe him the link to the scene. Our thanks.) When Connolly says that people are sometimes "too vain to do something badly" does he really mean they are to vain to do something bad?

I don't think so. He means they are too vain to do it badly, that is, less than perfectly. "Badly" modifies the doing, not the thing done. When we "feel bad", "bad" serves as the direct object of the verb to feel (bad is here what we feel). When we do something bad, "bad" is an adjective; it modifies the thing we are doing. When we feel badly, however, as the lady points out it, we are carrying out the act of feeling but we are doing a poor job of it. "Poor" is an adjective, of course; we can say the same thing with an adverb: "We are doing it poorly".

(An aside for my other blog: Poetry should make us feel better. I.e., it should make us better able to feel specific emotions, not filled with better feelings about particular subjects.)

Thomas wonders whether we should learn our grammar from Michelle Monaghan. Well, on this specific point she is right. But the careful reader/viewer will notice that she hasn't mastered the that/which distinction.