The second stanza relies heavily on repetition. Blake use the word “every” five times to suggest the overwhelming mood of the population. “Every ban” suggests government prohibitions of one sort or another. In the stanza he switches from the visual sense – what he can see – to the auditory – what he can hear. By the end of the stanza he can hear the “mind-forged manacles”; manacles are chains used to constrain criminals or prisoners, but these manacles are forged in the mind – it is as though the inhabitants of London do not even realize they are repressed.
In the third stanza he hears the cry of the chimney sweep and the soldier’s sigh which “runs in blood down palace walls.” In eighteenth century London young boys and girls were sold as slaves to master chimney sweeps to be sent up the chimneys of huge metropolitan houses: their life expectancy was very low. The “blackened church” is often read as a church blackened by pollution, but it might be a metaphor: the established Church, the Church of England, did nothing to protest about the slavery of young chimney sweeps. The soldier’s sigh running “in blood” is vague and cryptic, but it involves violence and the blood runs “down palace walls.” He seems to be protecting a royal palace.
The final stanza is the most hard-hitting and also the most cryptic. What Blake hears most often on the “midnight streets” is the cry of the “youthful harlot (a prostitute) who had given birth to unwanted baby. The harlot is angry: the bay is another mouth to feed and her curse blights the new-born infant’s tear and “blights with plagues the marriage hearse.” “Plagues" is often taken to refer to a sexually transmitted disease and the final oxymoron – the marriage hearse – associates marriage with death.
This poem is deeply critical of London in 1794 and deeply critical of the church and the royal family, whose palace the soldier dies defending. Blake had been deeply influenced by the American Revolution and the the French Revolution, and is writing as an English radical, critical of his capital city and the political establishment which allows people to live in such misery.