What is the author's tone in Much Madness Is Divinest Sense by Emily Dickinson?

Because she uses ambiguous words in this poem, it is difficult to determine the tone that Dickinson intended for "Much Madness Is Divinest Sense." Is she being cynical or humorous; is she depressed? Or is she writing these words because she has figured out the system and wants to pass the news along? Is she celebrating madness? Is she exposing the nonsense of those who claim to know what sanity is? The last line is rather disheartening with its image of the chain, but Dickinson could be ridiculing the oppressor. She could be telling them that despite their use of restraining devices, she is still free. After all, there is her reference to the divine in the first line. Also, regardless of the threats of the majority, Dickinson was able to write this poem, proving that their attempts to control her thoughts have failed.