by William Blake
While lots of Blake's speakers are kids, this one is most likely an adult male (and we're just assuming that since Blake was also a dude), a dude that is really unhappy with the state of things London. Okay, actually, he' s not just unhappy, he's downright fed up—bitter, angry, sad. He's getting tired of walking around London and hearing people cry, tired of hearing harlots curse, tired of seeing exploited children working as chimney sweeps, tired of everything that's bad about London.
More than just a dude who's sick of all the poverty and exploitation he sees around him, however, this speaker has some killer rhetorical skills and a corrosive, incisive ability to paint a picture that would move even the most unmovable of people. That whole stanza about the chimney sweeper's cry appalling every "blackning" church, for example, uses the color associated with chimneys (black) to make a claim about the church's moral "blackness." The soldier's sigh, a symbol of frustration or sadness or irritation, is the equivalent of blood running down the walls of the palace (the party responsible for wars, bloodshed, and the like).
Okay, lest you think our speaker is just some slightly bitter, unhappy guy who's a gifted rhetorician, let's throw into the mix, "somewhat of an idealist," in a good way. The whole reason the speaker is so upset with everything is because he has some idea of how things should be. Clearly, marriage shouldn't be a "hearse," children shouldn't be forced to work as chimney sweeps, soldiers shouldn't be sighing, harlots shouldn't be ruining the lives of little children, etc.
Even though the speaker doesn't tell us a lot about this ideal world, William Blake sure did, elsewhere that is. In some ways, this speaker is a mouthpiece for William Blake. Yeah, yeah—we know the speaker of a poem is not necessarily the equivalent of the author himself, but sometimes this distinction can be blurred a little bit. All of Blake's writings—other poems, letters, etc.—advance similar claims as "London." Blake made no secret of the fact that he hated child labor, war, and poverty, that he felt something was wrong with the church, and that he felt people were literally and figuratively enslaved. In sum, the speaker of this poem is a lot like William Blake sometimes, disturbed by what he sees, inspired to speak up and call attention to it.