In Blake’s time, poor parents often sold their children as ‘climbing boys’ to a master sweep at around the age of five. The boys were forced up narrow, winding chimneys to clean them of soot. Some suffocated inside the chimneys they were trying to clean; others grew up stunted and deformed, dying at a young age from cancer or lung diseases. Tom Dacre’s dream shows just how horrible this life was for the boys by contrasting it with what they should have been doing at this tender stage in their lives: ‘leaping’ and ‘laughing’ in the sunshine. The moral at the end of the poem is the statement of the young sweep who narrates the poem. Obviously it is nonsense: the climbing boys all ‘do their duty’ but still come to great harm. Yet the sweep is just innocently repeating the moral code which he has been taught by society. The poem thus holds a mirror up to its readers: it is you who deceive children with this false morality, just as it is ‘your chimneys’ (verse 1, line 4) that are responsible for having boy sweeps in the first place.